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    SubjectRe: [PATCH v3] mm, sysctl: make NUMA stats configurable
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    On 2017年09月29日 05:29, Andrew Morton wrote:
    > On Thu, 28 Sep 2017 14:11:41 +0800 Kemi Wang <kemi.wang@intel.com> wrote:
    >
    >> This is the second step which introduces a tunable interface that allow
    >> numa stats configurable for optimizing zone_statistics(), as suggested by
    >> Dave Hansen and Ying Huang.
    >
    > Looks OK I guess.
    >
    > I fiddled with it a lot. Please consider:
    >

    Thanks for your help to make it more graceful! I will be more careful next time.
    There may be a typo error in Documentation/sysctl/vm.txt, see comment below.

    > From: Andrew Morton <akpm@linux-foundation.org>
    > Subject: mm-sysctl-make-numa-stats-configurable-fix
    >
    > - tweak documentation
    >
    > - move advisory message from start_kernel() into mm_init() (I'm not sure
    > we really need this message)
    >
    > - use strcasecmp() in __parse_vm_numa_stats_mode()
    >
    > - clean up coding style amd nessages in sysctl_vm_numa_stats_mode_handler()
    >
    > Cc: Aaron Lu <aaron.lu@intel.com>
    > Cc: Andi Kleen <andi.kleen@intel.com>
    > Cc: Christopher Lameter <cl@linux.com>
    > Cc: Dave Hansen <dave.hansen@intel.com>
    > Cc: Jesper Dangaard Brouer <brouer@redhat.com>
    > Cc: Johannes Weiner <hannes@cmpxchg.org>
    > Cc: Jonathan Corbet <corbet@lwn.net>
    > Cc: Kees Cook <keescook@chromium.org>
    > Cc: Kemi Wang <kemi.wang@intel.com>
    > Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
    > Cc: Mel Gorman <mgorman@techsingularity.net>
    > Cc: Michal Hocko <mhocko@suse.com>
    > Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    > Cc: Tim Chen <tim.c.chen@intel.com>
    > Cc: Vlastimil Babka <vbabka@suse.cz>
    > Cc: Ying Huang <ying.huang@intel.com>
    > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    > ---
    >
    > Documentation/sysctl/vm.txt | 15 ++++++-------
    > init/main.c | 6 ++---
    > mm/vmstat.c | 39 +++++++++++++++-------------------
    > 3 files changed, 29 insertions(+), 31 deletions(-)
    >
    > diff -puN Documentation/sysctl/vm.txt~mm-sysctl-make-numa-stats-configurable-fix Documentation/sysctl/vm.txt
    > --- a/Documentation/sysctl/vm.txt~mm-sysctl-make-numa-stats-configurable-fix
    > +++ a/Documentation/sysctl/vm.txt
    > @@ -853,7 +853,7 @@ ten times more freeable objects than the
    >
    > numa_stats_mode
    >
    > -This interface allows numa statistics configurable.
    > +This interface allows runtime configuration *or* numa statistics.
    >

    typo? or->of/for?

    > When page allocation performance becomes a bottleneck and you can tolerate
    > some possible tool breakage and decreased numa counter precision, you can
    > @@ -864,13 +864,14 @@ When page allocation performance is not
    > tooling to work, you can do:
    > echo [S|s]trict > /proc/sys/vm/numa_stat_mode
    >
    > -We recommend automatic detection of numa statistics by system, because numa
    > -statistics does not affect system's decision and it is very rarely
    > -consumed. you can do:
    > +We recommend automatic detection of numa statistics by system, because
    > +numa statistics do not affect system decisions and it is very rarely
    > +consumed. In this case you can do:
    > echo [A|a]uto > /proc/sys/vm/numa_stats_mode
    > -This is also system default configuration, with this default setting, numa
    > -counters update is skipped unless the counter is *read* by users at least
    > -once.
    > +
    > +This is the system default configuration. With this default setting, numa
    > +counter updates are skipped until the counter is *read* by userspace at
    > +least once.
    >
    > ==============================================================
    >
    > diff -puN drivers/base/node.c~mm-sysctl-make-numa-stats-configurable-fix drivers/base/node.c
    > diff -puN include/linux/vmstat.h~mm-sysctl-make-numa-stats-configurable-fix include/linux/vmstat.h
    > diff -puN init/main.c~mm-sysctl-make-numa-stats-configurable-fix init/main.c
    > --- a/init/main.c~mm-sysctl-make-numa-stats-configurable-fix
    > +++ a/init/main.c
    > @@ -504,6 +504,9 @@ static void __init mm_init(void)
    > pgtable_init();
    > vmalloc_init();
    > ioremap_huge_init();
    > +#ifdef CONFIG_NUMA
    > + pr_info("vmstat: NUMA stat updates are skipped unless they have been used\n");
    > +#endif
    > }
    >
    > asmlinkage __visible void __init start_kernel(void)
    > @@ -567,9 +570,6 @@ asmlinkage __visible void __init start_k
    > sort_main_extable();
    > trap_init();
    > mm_init();
    > -#ifdef CONFIG_NUMA
    > - pr_info("vmstat: NUMA stats is skipped unless it has been consumed\n");
    > -#endif
    >
    > ftrace_init();
    >
    > diff -puN kernel/sysctl.c~mm-sysctl-make-numa-stats-configurable-fix kernel/sysctl.c
    > diff -puN mm/page_alloc.c~mm-sysctl-make-numa-stats-configurable-fix mm/page_alloc.c
    > diff -puN mm/vmstat.c~mm-sysctl-make-numa-stats-configurable-fix mm/vmstat.c
    > --- a/mm/vmstat.c~mm-sysctl-make-numa-stats-configurable-fix
    > +++ a/mm/vmstat.c
    > @@ -40,13 +40,11 @@ static DEFINE_MUTEX(vm_numa_stats_mode_l
    >
    > static int __parse_vm_numa_stats_mode(char *s)
    > {
    > - const char *str = s;
    > -
    > - if (strcmp(str, "auto") == 0 || strcmp(str, "Auto") == 0)
    > + if (strcasecmp(s, "auto"))
    > vm_numa_stats_mode = VM_NUMA_STAT_AUTO_MODE;
    > - else if (strcmp(str, "strict") == 0 || strcmp(str, "Strict") == 0)
    > + else if (strcasecmp(s, "strict") == 0)
    > vm_numa_stats_mode = VM_NUMA_STAT_STRICT_MODE;
    > - else if (strcmp(str, "coarse") == 0 || strcmp(str, "Coarse") == 0)
    > + else if (strcasecmp(s, "coarse"))
    > vm_numa_stats_mode = VM_NUMA_STAT_COARSE_MODE;
    > else {
    > pr_warn("Ignoring invalid vm_numa_stats_mode value: %s\n", s);
    > @@ -86,30 +84,29 @@ int sysctl_vm_numa_stats_mode_handler(st
    > /* no change */
    > mutex_unlock(&vm_numa_stats_mode_lock);
    > return 0;
    > - } else if (vm_numa_stats_mode == VM_NUMA_STAT_AUTO_MODE)
    > + } else if (vm_numa_stats_mode == VM_NUMA_STAT_AUTO_MODE) {
    > /*
    > - * Keep the branch selection in last time when numa stats
    > - * is changed to auto mode.
    > + * Keep the branch selection in last time when numa
    > + * stats is changed to auto mode.
    > */
    > - pr_info("numa stats changes from %s mode to auto mode\n",
    > - vm_numa_stats_mode_name[oldval]);
    > - else if (vm_numa_stats_mode == VM_NUMA_STAT_STRICT_MODE) {
    > + pr_info("numa stats changed from %s to auto mode\n",
    > + vm_numa_stats_mode_name[oldval]);
    > + } else if (vm_numa_stats_mode == VM_NUMA_STAT_STRICT_MODE) {
    > static_branch_enable(&vm_numa_stats_mode_key);
    > - pr_info("numa stats changes from %s mode to strict mode\n",
    > - vm_numa_stats_mode_name[oldval]);
    > + pr_info("numa stats changes from %s to strict mode\n",
    > + vm_numa_stats_mode_name[oldval]);
    > } else if (vm_numa_stats_mode == VM_NUMA_STAT_COARSE_MODE) {
    > static_branch_disable(&vm_numa_stats_mode_key);
    > /*
    > - * Invalidate numa counters when vmstat mode is set to coarse
    > - * mode, because users can't tell the difference between the
    > - * dead state and when allocator activity is quiet once
    > - * zone_statistics() is turned off.
    > + * Invalidate numa counters when vmstat mode is set to
    > + * coarse mode, because users can't tell the difference
    > + * between the dead state and when allocator activity is
    > + * quiet once zone_statistics() is turned off.
    > */
    > invalid_numa_statistics();
    > - pr_info("numa stats changes from %s mode to coarse mode\n",
    > - vm_numa_stats_mode_name[oldval]);
    > - } else
    > - pr_warn("invalid vm_numa_stats_mode:%d\n", vm_numa_stats_mode);
    > + pr_info("numa stats changes from %s to coarse mode\n",
    > + vm_numa_stats_mode_name[oldval]);
    > + }
    > }
    >
    > mutex_unlock(&vm_numa_stats_mode_lock);
    > _
    >

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