Revision 0ee931c4e31a5efb134c76440405e9219f896e33 authored by Michal Hocko on 13 September 2017, 23:28:29 UTC, committed by Linus Torvalds on 14 September 2017, 01:53:16 UTC
GFP_TEMPORARY was introduced by commit e12ba74d8ff3 ("Group short-lived and reclaimable kernel allocations") along with __GFP_RECLAIMABLE. It's primary motivation was to allow users to tell that an allocation is short lived and so the allocator can try to place such allocations close together and prevent long term fragmentation. As much as this sounds like a reasonable semantic it becomes much less clear when to use the highlevel GFP_TEMPORARY allocation flag. How long is temporary? Can the context holding that memory sleep? Can it take locks? It seems there is no good answer for those questions. The current implementation of GFP_TEMPORARY is basically GFP_KERNEL | __GFP_RECLAIMABLE which in itself is tricky because basically none of the existing caller provide a way to reclaim the allocated memory. So this is rather misleading and hard to evaluate for any benefits. I have checked some random users and none of them has added the flag with a specific justification. I suspect most of them just copied from other existing users and others just thought it might be a good idea to use without any measuring. This suggests that GFP_TEMPORARY just motivates for cargo cult usage without any reasoning. I believe that our gfp flags are quite complex already and especially those with highlevel semantic should be clearly defined to prevent from confusion and abuse. Therefore I propose dropping GFP_TEMPORARY and replace all existing users to simply use GFP_KERNEL. Please note that SLAB users with shrinkers will still get __GFP_RECLAIMABLE heuristic and so they will be placed properly for memory fragmentation prevention. I can see reasons we might want some gfp flag to reflect shorterm allocations but I propose starting from a clear semantic definition and only then add users with proper justification. This was been brought up before LSF this year by Matthew [1] and it turned out that GFP_TEMPORARY really doesn't have a clear semantic. It seems to be a heuristic without any measured advantage for most (if not all) its current users. The follow up discussion has revealed that opinions on what might be temporary allocation differ a lot between developers. So rather than trying to tweak existing users into a semantic which they haven't expected I propose to simply remove the flag and start from scratch if we really need a semantic for short term allocations. [1] http://lkml.kernel.org/r/20170118054945.GD18349@bombadil.infradead.org [akpm@linux-foundation.org: fix typo] [akpm@linux-foundation.org: coding-style fixes] [sfr@canb.auug.org.au: drm/i915: fix up] Link: http://lkml.kernel.org/r/20170816144703.378d4f4d@canb.auug.org.au Link: http://lkml.kernel.org/r/20170728091904.14627-1-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Matthew Wilcox <willy@infradead.org> Cc: Neil Brown <neilb@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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qconf.h
/*
* Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
* Released under the terms of the GNU GPL v2.0.
*/
#include <QTextBrowser>
#include <QTreeWidget>
#include <QMainWindow>
#include <QHeaderView>
#include <qsettings.h>
#include <QPushButton>
#include <QSettings>
#include <QLineEdit>
#include <QSplitter>
#include <QCheckBox>
#include <QDialog>
#include "expr.h"
class ConfigView;
class ConfigList;
class ConfigItem;
class ConfigLineEdit;
class ConfigMainWindow;
class ConfigSettings : public QSettings {
public:
ConfigSettings();
QList<int> readSizes(const QString& key, bool *ok);
bool writeSizes(const QString& key, const QList<int>& value);
};
enum colIdx {
promptColIdx, nameColIdx, noColIdx, modColIdx, yesColIdx, dataColIdx, colNr
};
enum listMode {
singleMode, menuMode, symbolMode, fullMode, listMode
};
enum optionMode {
normalOpt = 0, allOpt, promptOpt
};
class ConfigList : public QTreeWidget {
Q_OBJECT
typedef class QTreeWidget Parent;
public:
ConfigList(ConfigView* p, const char *name = 0);
void reinit(void);
ConfigView* parent(void) const
{
return (ConfigView*)Parent::parent();
}
ConfigItem* findConfigItem(struct menu *);
protected:
void keyPressEvent(QKeyEvent *e);
void mousePressEvent(QMouseEvent *e);
void mouseReleaseEvent(QMouseEvent *e);
void mouseMoveEvent(QMouseEvent *e);
void mouseDoubleClickEvent(QMouseEvent *e);
void focusInEvent(QFocusEvent *e);
void contextMenuEvent(QContextMenuEvent *e);
public slots:
void setRootMenu(struct menu *menu);
void updateList(ConfigItem *item);
void setValue(ConfigItem* item, tristate val);
void changeValue(ConfigItem* item);
void updateSelection(void);
void saveSettings(void);
signals:
void menuChanged(struct menu *menu);
void menuSelected(struct menu *menu);
void parentSelected(void);
void gotFocus(struct menu *);
public:
void updateListAll(void)
{
updateAll = true;
updateList(NULL);
updateAll = false;
}
ConfigList* listView()
{
return this;
}
ConfigItem* firstChild() const
{
return (ConfigItem *)children().first();
}
void addColumn(colIdx idx)
{
showColumn(idx);
}
void removeColumn(colIdx idx)
{
hideColumn(idx);
}
void setAllOpen(bool open);
void setParentMenu(void);
bool menuSkip(struct menu *);
void updateMenuList(ConfigItem *parent, struct menu*);
void updateMenuList(ConfigList *parent, struct menu*);
bool updateAll;
QPixmap symbolYesPix, symbolModPix, symbolNoPix;
QPixmap choiceYesPix, choiceNoPix;
QPixmap menuPix, menuInvPix, menuBackPix, voidPix;
bool showName, showRange, showData;
enum listMode mode;
enum optionMode optMode;
struct menu *rootEntry;
QPalette disabledColorGroup;
QPalette inactivedColorGroup;
QMenu* headerPopup;
};
class ConfigItem : public QTreeWidgetItem {
typedef class QTreeWidgetItem Parent;
public:
ConfigItem(ConfigList *parent, ConfigItem *after, struct menu *m, bool v)
: Parent(parent, after), nextItem(0), menu(m), visible(v), goParent(false)
{
init();
}
ConfigItem(ConfigItem *parent, ConfigItem *after, struct menu *m, bool v)
: Parent(parent, after), nextItem(0), menu(m), visible(v), goParent(false)
{
init();
}
ConfigItem(ConfigList *parent, ConfigItem *after, bool v)
: Parent(parent, after), nextItem(0), menu(0), visible(v), goParent(true)
{
init();
}
~ConfigItem(void);
void init(void);
void okRename(int col);
void updateMenu(void);
void testUpdateMenu(bool v);
ConfigList* listView() const
{
return (ConfigList*)Parent::treeWidget();
}
ConfigItem* firstChild() const
{
return (ConfigItem *)Parent::child(0);
}
ConfigItem* nextSibling()
{
ConfigItem *ret = NULL;
ConfigItem *_parent = (ConfigItem *)parent();
if(_parent) {
ret = (ConfigItem *)_parent->child(_parent->indexOfChild(this)+1);
} else {
QTreeWidget *_treeWidget = treeWidget();
ret = (ConfigItem *)_treeWidget->topLevelItem(_treeWidget->indexOfTopLevelItem(this)+1);
}
return ret;
}
void setText(colIdx idx, const QString& text)
{
Parent::setText(idx, text);
}
QString text(colIdx idx) const
{
return Parent::text(idx);
}
void setPixmap(colIdx idx, const QIcon &icon)
{
Parent::setIcon(idx, icon);
}
const QIcon pixmap(colIdx idx) const
{
return icon(idx);
}
// TODO: Implement paintCell
ConfigItem* nextItem;
struct menu *menu;
bool visible;
bool goParent;
};
class ConfigLineEdit : public QLineEdit {
Q_OBJECT
typedef class QLineEdit Parent;
public:
ConfigLineEdit(ConfigView* parent);
ConfigView* parent(void) const
{
return (ConfigView*)Parent::parent();
}
void show(ConfigItem *i);
void keyPressEvent(QKeyEvent *e);
public:
ConfigItem *item;
};
class ConfigView : public QWidget {
Q_OBJECT
typedef class QWidget Parent;
public:
ConfigView(QWidget* parent, const char *name = 0);
~ConfigView(void);
static void updateList(ConfigItem* item);
static void updateListAll(void);
bool showName(void) const { return list->showName; }
bool showRange(void) const { return list->showRange; }
bool showData(void) const { return list->showData; }
public slots:
void setShowName(bool);
void setShowRange(bool);
void setShowData(bool);
void setOptionMode(QAction *);
signals:
void showNameChanged(bool);
void showRangeChanged(bool);
void showDataChanged(bool);
public:
ConfigList* list;
ConfigLineEdit* lineEdit;
static ConfigView* viewList;
ConfigView* nextView;
static QAction *showNormalAction;
static QAction *showAllAction;
static QAction *showPromptAction;
};
class ConfigInfoView : public QTextBrowser {
Q_OBJECT
typedef class QTextBrowser Parent;
public:
ConfigInfoView(QWidget* parent, const char *name = 0);
bool showDebug(void) const { return _showDebug; }
public slots:
void setInfo(struct menu *menu);
void saveSettings(void);
void setShowDebug(bool);
signals:
void showDebugChanged(bool);
void menuSelected(struct menu *);
protected:
void symbolInfo(void);
void menuInfo(void);
QString debug_info(struct symbol *sym);
static QString print_filter(const QString &str);
static void expr_print_help(void *data, struct symbol *sym, const char *str);
QMenu *createStandardContextMenu(const QPoint & pos);
void contextMenuEvent(QContextMenuEvent *e);
struct symbol *sym;
struct menu *_menu;
bool _showDebug;
};
class ConfigSearchWindow : public QDialog {
Q_OBJECT
typedef class QDialog Parent;
public:
ConfigSearchWindow(ConfigMainWindow* parent, const char *name = 0);
public slots:
void saveSettings(void);
void search(void);
protected:
QLineEdit* editField;
QPushButton* searchButton;
QSplitter* split;
ConfigView* list;
ConfigInfoView* info;
struct symbol **result;
};
class ConfigMainWindow : public QMainWindow {
Q_OBJECT
static QAction *saveAction;
static void conf_changed(void);
public:
ConfigMainWindow(void);
public slots:
void changeMenu(struct menu *);
void setMenuLink(struct menu *);
void listFocusChanged(void);
void goBack(void);
void loadConfig(void);
bool saveConfig(void);
void saveConfigAs(void);
void searchConfig(void);
void showSingleView(void);
void showSplitView(void);
void showFullView(void);
void showIntro(void);
void showAbout(void);
void saveSettings(void);
protected:
void closeEvent(QCloseEvent *e);
ConfigSearchWindow *searchWindow;
ConfigView *menuView;
ConfigList *menuList;
ConfigView *configView;
ConfigList *configList;
ConfigInfoView *helpText;
QToolBar *toolBar;
QAction *backAction;
QAction *singleViewAction;
QAction *splitViewAction;
QAction *fullViewAction;
QSplitter *split1;
QSplitter *split2;
};
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