Revision c4f675cd40d955d539180506c09515c90169b15b authored by Sergei Trofimovich on 20 May 2011, 20:20:30 UTC, committed by Chris Mason on 23 May 2011, 17:24:14 UTC
Observed as a large delay when --mixed filesystem is filled up.
Test example:
1. create tiny --mixed FS:
$ dd if=/dev/zero of=2G.img seek=$((2048 * 1024 * 1024 - 1)) count=1 bs=1
$ mkfs.btrfs --mixed 2G.img
$ mount -oloop 2G.img /mnt/ut/
2. Try to fill it up:
$ dd if=/dev/urandom of=10M.file bs=10240 count=1024
$ seq 1 256 | while read file_no; do echo $file_no; time cp 10M.file ${file_no}.copy; done
Up to '200.copy' it goes fast, but when disk fills-up each -ENOSPC
message takes 3 seconds to pop-up _every_ ENOSPC (and in usermode linux
it's even more: 30-60 seconds!). (Maybe, time depends on kernel's timer resolution).
No IO, no CPU load, just rescheduling. Some debugging revealed busy spinning
in shrink_delalloc.
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Reviewed-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
1 parent 0f3b708
udelay.c
/*
* Copyright (C) 1993, 2000 Linus Torvalds
*
* Delay routines, using a pre-computed "loops_per_jiffy" value.
*/
#include <linux/module.h>
#include <linux/sched.h> /* for udelay's use of smp_processor_id */
#include <asm/param.h>
#include <asm/smp.h>
#include <linux/delay.h>
/*
* Use only for very small delays (< 1 msec).
*
* The active part of our cycle counter is only 32-bits wide, and
* we're treating the difference between two marks as signed. On
* a 1GHz box, that's about 2 seconds.
*/
void
__delay(int loops)
{
int tmp;
__asm__ __volatile__(
" rpcc %0\n"
" addl %1,%0,%1\n"
"1: rpcc %0\n"
" subl %1,%0,%0\n"
" bgt %0,1b"
: "=&r" (tmp), "=r" (loops) : "1"(loops));
}
#ifdef CONFIG_SMP
#define LPJ cpu_data[smp_processor_id()].loops_per_jiffy
#else
#define LPJ loops_per_jiffy
#endif
void
udelay(unsigned long usecs)
{
usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
__delay((long)usecs >> 32);
}
EXPORT_SYMBOL(udelay);
void
ndelay(unsigned long nsecs)
{
nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
__delay((long)nsecs >> 32);
}
EXPORT_SYMBOL(ndelay);
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