Revision 3808d34838184fd29088d6b3a364ba2f1c018fb6 authored by Stanislaw Gruszka on 02 February 2017, 12:32:10 UTC, committed by David S. Miller on 03 February 2017, 16:13:00 UTC
If ->get_regs_len() callback return 0, we allocate 0 bytes of memory, what print ugly warning in dmesg, which can be found further below. This happen on mac80211 devices where ieee80211_get_regs_len() just return 0 and driver only fills ethtool_regs structure and actually do not provide any dump. However I assume this can happen on other drivers i.e. when for some devices driver provide regs dump and for others do not. Hence preventing to to print warning in ethtool code seems to be reasonable. ethtool: vmalloc: allocation failure: 0 bytes, mode:0x24080c2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_ZERO) <snip> Call Trace: [<ffffffff813bde47>] dump_stack+0x63/0x8c [<ffffffff811b0a1f>] warn_alloc+0x13f/0x170 [<ffffffff811f0476>] __vmalloc_node_range+0x1e6/0x2c0 [<ffffffff811f0874>] vzalloc+0x54/0x60 [<ffffffff8169986c>] dev_ethtool+0xb4c/0x1b30 [<ffffffff816adbb1>] dev_ioctl+0x181/0x520 [<ffffffff816714d2>] sock_do_ioctl+0x42/0x50 <snip> Mem-Info: active_anon:435809 inactive_anon:173951 isolated_anon:0 active_file:835822 inactive_file:196932 isolated_file:0 unevictable:0 dirty:8 writeback:0 unstable:0 slab_reclaimable:157732 slab_unreclaimable:10022 mapped:83042 shmem:306356 pagetables:9507 bounce:0 free:130041 free_pcp:1080 free_cma:0 Node 0 active_anon:1743236kB inactive_anon:695804kB active_file:3343288kB inactive_file:787728kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:332168kB dirty:32kB writeback:0kB shmem:0kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 1225424kB writeback_tmp:0kB unstable:0kB pages_scanned:0 all_unreclaimable? no Node 0 DMA free:15900kB min:136kB low:168kB high:200kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15984kB managed:15900kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB lowmem_reserve[]: 0 3187 7643 7643 Node 0 DMA32 free:419732kB min:28124kB low:35152kB high:42180kB active_anon:541180kB inactive_anon:248988kB active_file:1466388kB inactive_file:389632kB unevictable:0kB writepending:0kB present:3370280kB managed:3290932kB mlocked:0kB slab_reclaimable:217184kB slab_unreclaimable:4180kB kernel_stack:160kB pagetables:984kB bounce:0kB free_pcp:2236kB local_pcp:660kB free_cma:0kB lowmem_reserve[]: 0 0 4456 4456 Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent 013e816
blk-wbt.c
/*
* buffered writeback throttling. loosely based on CoDel. We can't drop
* packets for IO scheduling, so the logic is something like this:
*
* - Monitor latencies in a defined window of time.
* - If the minimum latency in the above window exceeds some target, increment
* scaling step and scale down queue depth by a factor of 2x. The monitoring
* window is then shrunk to 100 / sqrt(scaling step + 1).
* - For any window where we don't have solid data on what the latencies
* look like, retain status quo.
* - If latencies look good, decrement scaling step.
* - If we're only doing writes, allow the scaling step to go negative. This
* will temporarily boost write performance, snapping back to a stable
* scaling step of 0 if reads show up or the heavy writers finish. Unlike
* positive scaling steps where we shrink the monitoring window, a negative
* scaling step retains the default step==0 window size.
*
* Copyright (C) 2016 Jens Axboe
*
*/
#include <linux/kernel.h>
#include <linux/blk_types.h>
#include <linux/slab.h>
#include <linux/backing-dev.h>
#include <linux/swap.h>
#include "blk-wbt.h"
#define CREATE_TRACE_POINTS
#include <trace/events/wbt.h>
enum {
/*
* Default setting, we'll scale up (to 75% of QD max) or down (min 1)
* from here depending on device stats
*/
RWB_DEF_DEPTH = 16,
/*
* 100msec window
*/
RWB_WINDOW_NSEC = 100 * 1000 * 1000ULL,
/*
* Disregard stats, if we don't meet this minimum
*/
RWB_MIN_WRITE_SAMPLES = 3,
/*
* If we have this number of consecutive windows with not enough
* information to scale up or down, scale up.
*/
RWB_UNKNOWN_BUMP = 5,
};
static inline bool rwb_enabled(struct rq_wb *rwb)
{
return rwb && rwb->wb_normal != 0;
}
/*
* Increment 'v', if 'v' is below 'below'. Returns true if we succeeded,
* false if 'v' + 1 would be bigger than 'below'.
*/
static bool atomic_inc_below(atomic_t *v, int below)
{
int cur = atomic_read(v);
for (;;) {
int old;
if (cur >= below)
return false;
old = atomic_cmpxchg(v, cur, cur + 1);
if (old == cur)
break;
cur = old;
}
return true;
}
static void wb_timestamp(struct rq_wb *rwb, unsigned long *var)
{
if (rwb_enabled(rwb)) {
const unsigned long cur = jiffies;
if (cur != *var)
*var = cur;
}
}
/*
* If a task was rate throttled in balance_dirty_pages() within the last
* second or so, use that to indicate a higher cleaning rate.
*/
static bool wb_recent_wait(struct rq_wb *rwb)
{
struct bdi_writeback *wb = &rwb->queue->backing_dev_info.wb;
return time_before(jiffies, wb->dirty_sleep + HZ);
}
static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, bool is_kswapd)
{
return &rwb->rq_wait[is_kswapd];
}
static void rwb_wake_all(struct rq_wb *rwb)
{
int i;
for (i = 0; i < WBT_NUM_RWQ; i++) {
struct rq_wait *rqw = &rwb->rq_wait[i];
if (waitqueue_active(&rqw->wait))
wake_up_all(&rqw->wait);
}
}
void __wbt_done(struct rq_wb *rwb, enum wbt_flags wb_acct)
{
struct rq_wait *rqw;
int inflight, limit;
if (!(wb_acct & WBT_TRACKED))
return;
rqw = get_rq_wait(rwb, wb_acct & WBT_KSWAPD);
inflight = atomic_dec_return(&rqw->inflight);
/*
* wbt got disabled with IO in flight. Wake up any potential
* waiters, we don't have to do more than that.
*/
if (unlikely(!rwb_enabled(rwb))) {
rwb_wake_all(rwb);
return;
}
/*
* If the device does write back caching, drop further down
* before we wake people up.
*/
if (rwb->wc && !wb_recent_wait(rwb))
limit = 0;
else
limit = rwb->wb_normal;
/*
* Don't wake anyone up if we are above the normal limit.
*/
if (inflight && inflight >= limit)
return;
if (waitqueue_active(&rqw->wait)) {
int diff = limit - inflight;
if (!inflight || diff >= rwb->wb_background / 2)
wake_up_all(&rqw->wait);
}
}
/*
* Called on completion of a request. Note that it's also called when
* a request is merged, when the request gets freed.
*/
void wbt_done(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
if (!rwb)
return;
if (!wbt_is_tracked(stat)) {
if (rwb->sync_cookie == stat) {
rwb->sync_issue = 0;
rwb->sync_cookie = NULL;
}
if (wbt_is_read(stat))
wb_timestamp(rwb, &rwb->last_comp);
wbt_clear_state(stat);
} else {
WARN_ON_ONCE(stat == rwb->sync_cookie);
__wbt_done(rwb, wbt_stat_to_mask(stat));
wbt_clear_state(stat);
}
}
/*
* Return true, if we can't increase the depth further by scaling
*/
static bool calc_wb_limits(struct rq_wb *rwb)
{
unsigned int depth;
bool ret = false;
if (!rwb->min_lat_nsec) {
rwb->wb_max = rwb->wb_normal = rwb->wb_background = 0;
return false;
}
/*
* For QD=1 devices, this is a special case. It's important for those
* to have one request ready when one completes, so force a depth of
* 2 for those devices. On the backend, it'll be a depth of 1 anyway,
* since the device can't have more than that in flight. If we're
* scaling down, then keep a setting of 1/1/1.
*/
if (rwb->queue_depth == 1) {
if (rwb->scale_step > 0)
rwb->wb_max = rwb->wb_normal = 1;
else {
rwb->wb_max = rwb->wb_normal = 2;
ret = true;
}
rwb->wb_background = 1;
} else {
/*
* scale_step == 0 is our default state. If we have suffered
* latency spikes, step will be > 0, and we shrink the
* allowed write depths. If step is < 0, we're only doing
* writes, and we allow a temporarily higher depth to
* increase performance.
*/
depth = min_t(unsigned int, RWB_DEF_DEPTH, rwb->queue_depth);
if (rwb->scale_step > 0)
depth = 1 + ((depth - 1) >> min(31, rwb->scale_step));
else if (rwb->scale_step < 0) {
unsigned int maxd = 3 * rwb->queue_depth / 4;
depth = 1 + ((depth - 1) << -rwb->scale_step);
if (depth > maxd) {
depth = maxd;
ret = true;
}
}
/*
* Set our max/normal/bg queue depths based on how far
* we have scaled down (->scale_step).
*/
rwb->wb_max = depth;
rwb->wb_normal = (rwb->wb_max + 1) / 2;
rwb->wb_background = (rwb->wb_max + 3) / 4;
}
return ret;
}
static inline bool stat_sample_valid(struct blk_rq_stat *stat)
{
/*
* We need at least one read sample, and a minimum of
* RWB_MIN_WRITE_SAMPLES. We require some write samples to know
* that it's writes impacting us, and not just some sole read on
* a device that is in a lower power state.
*/
return stat[BLK_STAT_READ].nr_samples >= 1 &&
stat[BLK_STAT_WRITE].nr_samples >= RWB_MIN_WRITE_SAMPLES;
}
static u64 rwb_sync_issue_lat(struct rq_wb *rwb)
{
u64 now, issue = ACCESS_ONCE(rwb->sync_issue);
if (!issue || !rwb->sync_cookie)
return 0;
now = ktime_to_ns(ktime_get());
return now - issue;
}
enum {
LAT_OK = 1,
LAT_UNKNOWN,
LAT_UNKNOWN_WRITES,
LAT_EXCEEDED,
};
static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
{
struct backing_dev_info *bdi = &rwb->queue->backing_dev_info;
u64 thislat;
/*
* If our stored sync issue exceeds the window size, or it
* exceeds our min target AND we haven't logged any entries,
* flag the latency as exceeded. wbt works off completion latencies,
* but for a flooded device, a single sync IO can take a long time
* to complete after being issued. If this time exceeds our
* monitoring window AND we didn't see any other completions in that
* window, then count that sync IO as a violation of the latency.
*/
thislat = rwb_sync_issue_lat(rwb);
if (thislat > rwb->cur_win_nsec ||
(thislat > rwb->min_lat_nsec && !stat[BLK_STAT_READ].nr_samples)) {
trace_wbt_lat(bdi, thislat);
return LAT_EXCEEDED;
}
/*
* No read/write mix, if stat isn't valid
*/
if (!stat_sample_valid(stat)) {
/*
* If we had writes in this stat window and the window is
* current, we're only doing writes. If a task recently
* waited or still has writes in flights, consider us doing
* just writes as well.
*/
if ((stat[BLK_STAT_WRITE].nr_samples && blk_stat_is_current(stat)) ||
wb_recent_wait(rwb) || wbt_inflight(rwb))
return LAT_UNKNOWN_WRITES;
return LAT_UNKNOWN;
}
/*
* If the 'min' latency exceeds our target, step down.
*/
if (stat[BLK_STAT_READ].min > rwb->min_lat_nsec) {
trace_wbt_lat(bdi, stat[BLK_STAT_READ].min);
trace_wbt_stat(bdi, stat);
return LAT_EXCEEDED;
}
if (rwb->scale_step)
trace_wbt_stat(bdi, stat);
return LAT_OK;
}
static int latency_exceeded(struct rq_wb *rwb)
{
struct blk_rq_stat stat[2];
blk_queue_stat_get(rwb->queue, stat);
return __latency_exceeded(rwb, stat);
}
static void rwb_trace_step(struct rq_wb *rwb, const char *msg)
{
struct backing_dev_info *bdi = &rwb->queue->backing_dev_info;
trace_wbt_step(bdi, msg, rwb->scale_step, rwb->cur_win_nsec,
rwb->wb_background, rwb->wb_normal, rwb->wb_max);
}
static void scale_up(struct rq_wb *rwb)
{
/*
* Hit max in previous round, stop here
*/
if (rwb->scaled_max)
return;
rwb->scale_step--;
rwb->unknown_cnt = 0;
blk_stat_clear(rwb->queue);
rwb->scaled_max = calc_wb_limits(rwb);
rwb_wake_all(rwb);
rwb_trace_step(rwb, "step up");
}
/*
* Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
* had a latency violation.
*/
static void scale_down(struct rq_wb *rwb, bool hard_throttle)
{
/*
* Stop scaling down when we've hit the limit. This also prevents
* ->scale_step from going to crazy values, if the device can't
* keep up.
*/
if (rwb->wb_max == 1)
return;
if (rwb->scale_step < 0 && hard_throttle)
rwb->scale_step = 0;
else
rwb->scale_step++;
rwb->scaled_max = false;
rwb->unknown_cnt = 0;
blk_stat_clear(rwb->queue);
calc_wb_limits(rwb);
rwb_trace_step(rwb, "step down");
}
static void rwb_arm_timer(struct rq_wb *rwb)
{
unsigned long expires;
if (rwb->scale_step > 0) {
/*
* We should speed this up, using some variant of a fast
* integer inverse square root calculation. Since we only do
* this for every window expiration, it's not a huge deal,
* though.
*/
rwb->cur_win_nsec = div_u64(rwb->win_nsec << 4,
int_sqrt((rwb->scale_step + 1) << 8));
} else {
/*
* For step < 0, we don't want to increase/decrease the
* window size.
*/
rwb->cur_win_nsec = rwb->win_nsec;
}
expires = jiffies + nsecs_to_jiffies(rwb->cur_win_nsec);
mod_timer(&rwb->window_timer, expires);
}
static void wb_timer_fn(unsigned long data)
{
struct rq_wb *rwb = (struct rq_wb *) data;
unsigned int inflight = wbt_inflight(rwb);
int status;
status = latency_exceeded(rwb);
trace_wbt_timer(&rwb->queue->backing_dev_info, status, rwb->scale_step,
inflight);
/*
* If we exceeded the latency target, step down. If we did not,
* step one level up. If we don't know enough to say either exceeded
* or ok, then don't do anything.
*/
switch (status) {
case LAT_EXCEEDED:
scale_down(rwb, true);
break;
case LAT_OK:
scale_up(rwb);
break;
case LAT_UNKNOWN_WRITES:
/*
* We started a the center step, but don't have a valid
* read/write sample, but we do have writes going on.
* Allow step to go negative, to increase write perf.
*/
scale_up(rwb);
break;
case LAT_UNKNOWN:
if (++rwb->unknown_cnt < RWB_UNKNOWN_BUMP)
break;
/*
* We get here when previously scaled reduced depth, and we
* currently don't have a valid read/write sample. For that
* case, slowly return to center state (step == 0).
*/
if (rwb->scale_step > 0)
scale_up(rwb);
else if (rwb->scale_step < 0)
scale_down(rwb, false);
break;
default:
break;
}
/*
* Re-arm timer, if we have IO in flight
*/
if (rwb->scale_step || inflight)
rwb_arm_timer(rwb);
}
void wbt_update_limits(struct rq_wb *rwb)
{
rwb->scale_step = 0;
rwb->scaled_max = false;
calc_wb_limits(rwb);
rwb_wake_all(rwb);
}
static bool close_io(struct rq_wb *rwb)
{
const unsigned long now = jiffies;
return time_before(now, rwb->last_issue + HZ / 10) ||
time_before(now, rwb->last_comp + HZ / 10);
}
#define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO)
static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw)
{
unsigned int limit;
/*
* At this point we know it's a buffered write. If this is
* kswapd trying to free memory, or REQ_SYNC is set, set, then
* it's WB_SYNC_ALL writeback, and we'll use the max limit for
* that. If the write is marked as a background write, then use
* the idle limit, or go to normal if we haven't had competing
* IO for a bit.
*/
if ((rw & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd())
limit = rwb->wb_max;
else if ((rw & REQ_BACKGROUND) || close_io(rwb)) {
/*
* If less than 100ms since we completed unrelated IO,
* limit us to half the depth for background writeback.
*/
limit = rwb->wb_background;
} else
limit = rwb->wb_normal;
return limit;
}
static inline bool may_queue(struct rq_wb *rwb, struct rq_wait *rqw,
wait_queue_t *wait, unsigned long rw)
{
/*
* inc it here even if disabled, since we'll dec it at completion.
* this only happens if the task was sleeping in __wbt_wait(),
* and someone turned it off at the same time.
*/
if (!rwb_enabled(rwb)) {
atomic_inc(&rqw->inflight);
return true;
}
/*
* If the waitqueue is already active and we are not the next
* in line to be woken up, wait for our turn.
*/
if (waitqueue_active(&rqw->wait) &&
rqw->wait.task_list.next != &wait->task_list)
return false;
return atomic_inc_below(&rqw->inflight, get_limit(rwb, rw));
}
/*
* Block if we will exceed our limit, or if we are currently waiting for
* the timer to kick off queuing again.
*/
static void __wbt_wait(struct rq_wb *rwb, unsigned long rw, spinlock_t *lock)
__releases(lock)
__acquires(lock)
{
struct rq_wait *rqw = get_rq_wait(rwb, current_is_kswapd());
DEFINE_WAIT(wait);
if (may_queue(rwb, rqw, &wait, rw))
return;
do {
prepare_to_wait_exclusive(&rqw->wait, &wait,
TASK_UNINTERRUPTIBLE);
if (may_queue(rwb, rqw, &wait, rw))
break;
if (lock) {
spin_unlock_irq(lock);
io_schedule();
spin_lock_irq(lock);
} else
io_schedule();
} while (1);
finish_wait(&rqw->wait, &wait);
}
static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio)
{
const int op = bio_op(bio);
/*
* If not a WRITE, do nothing
*/
if (op != REQ_OP_WRITE)
return false;
/*
* Don't throttle WRITE_ODIRECT
*/
if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) == (REQ_SYNC | REQ_IDLE))
return false;
return true;
}
/*
* Returns true if the IO request should be accounted, false if not.
* May sleep, if we have exceeded the writeback limits. Caller can pass
* in an irq held spinlock, if it holds one when calling this function.
* If we do sleep, we'll release and re-grab it.
*/
enum wbt_flags wbt_wait(struct rq_wb *rwb, struct bio *bio, spinlock_t *lock)
{
unsigned int ret = 0;
if (!rwb_enabled(rwb))
return 0;
if (bio_op(bio) == REQ_OP_READ)
ret = WBT_READ;
if (!wbt_should_throttle(rwb, bio)) {
if (ret & WBT_READ)
wb_timestamp(rwb, &rwb->last_issue);
return ret;
}
__wbt_wait(rwb, bio->bi_opf, lock);
if (!timer_pending(&rwb->window_timer))
rwb_arm_timer(rwb);
if (current_is_kswapd())
ret |= WBT_KSWAPD;
return ret | WBT_TRACKED;
}
void wbt_issue(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
if (!rwb_enabled(rwb))
return;
/*
* Track sync issue, in case it takes a long time to complete. Allows
* us to react quicker, if a sync IO takes a long time to complete.
* Note that this is just a hint. 'stat' can go away when the
* request completes, so it's important we never dereference it. We
* only use the address to compare with, which is why we store the
* sync_issue time locally.
*/
if (wbt_is_read(stat) && !rwb->sync_issue) {
rwb->sync_cookie = stat;
rwb->sync_issue = blk_stat_time(stat);
}
}
void wbt_requeue(struct rq_wb *rwb, struct blk_issue_stat *stat)
{
if (!rwb_enabled(rwb))
return;
if (stat == rwb->sync_cookie) {
rwb->sync_issue = 0;
rwb->sync_cookie = NULL;
}
}
void wbt_set_queue_depth(struct rq_wb *rwb, unsigned int depth)
{
if (rwb) {
rwb->queue_depth = depth;
wbt_update_limits(rwb);
}
}
void wbt_set_write_cache(struct rq_wb *rwb, bool write_cache_on)
{
if (rwb)
rwb->wc = write_cache_on;
}
/*
* Disable wbt, if enabled by default. Only called from CFQ, if we have
* cgroups enabled
*/
void wbt_disable_default(struct request_queue *q)
{
struct rq_wb *rwb = q->rq_wb;
if (rwb && rwb->enable_state == WBT_STATE_ON_DEFAULT) {
del_timer_sync(&rwb->window_timer);
rwb->win_nsec = rwb->min_lat_nsec = 0;
wbt_update_limits(rwb);
}
}
EXPORT_SYMBOL_GPL(wbt_disable_default);
u64 wbt_default_latency_nsec(struct request_queue *q)
{
/*
* We default to 2msec for non-rotational storage, and 75msec
* for rotational storage.
*/
if (blk_queue_nonrot(q))
return 2000000ULL;
else
return 75000000ULL;
}
int wbt_init(struct request_queue *q)
{
struct rq_wb *rwb;
int i;
/*
* For now, we depend on the stats window being larger than
* our monitoring window. Ensure that this isn't inadvertently
* violated.
*/
BUILD_BUG_ON(RWB_WINDOW_NSEC > BLK_STAT_NSEC);
BUILD_BUG_ON(WBT_NR_BITS > BLK_STAT_RES_BITS);
rwb = kzalloc(sizeof(*rwb), GFP_KERNEL);
if (!rwb)
return -ENOMEM;
for (i = 0; i < WBT_NUM_RWQ; i++) {
atomic_set(&rwb->rq_wait[i].inflight, 0);
init_waitqueue_head(&rwb->rq_wait[i].wait);
}
setup_timer(&rwb->window_timer, wb_timer_fn, (unsigned long) rwb);
rwb->wc = 1;
rwb->queue_depth = RWB_DEF_DEPTH;
rwb->last_comp = rwb->last_issue = jiffies;
rwb->queue = q;
rwb->win_nsec = RWB_WINDOW_NSEC;
rwb->enable_state = WBT_STATE_ON_DEFAULT;
wbt_update_limits(rwb);
/*
* Assign rwb, and turn on stats tracking for this queue
*/
q->rq_wb = rwb;
blk_stat_enable(q);
rwb->min_lat_nsec = wbt_default_latency_nsec(q);
wbt_set_queue_depth(rwb, blk_queue_depth(q));
wbt_set_write_cache(rwb, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
return 0;
}
void wbt_exit(struct request_queue *q)
{
struct rq_wb *rwb = q->rq_wb;
if (rwb) {
del_timer_sync(&rwb->window_timer);
q->rq_wb = NULL;
kfree(rwb);
}
}
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...