From: Dave Hansen <dave.hansen@intel.com>
To: Saravanan D <saravanand@outlook.com>,
x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org,
peterz@infradead.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH] x86/mm: Tracking linear mapping split events since boot
Date: Mon, 25 Jan 2021 12:15:51 -0800 [thread overview]
Message-ID: <30752f8e-16e9-d093-e6ec-31fd45715e9d@intel.com> (raw)
In-Reply-To: <BYAPR01MB40856478D5BE74CB6A7D5578CFBD9@BYAPR01MB4085.prod.exchangelabs.com>
On 1/25/21 12:11 PM, Saravanan D wrote:
> Numerous hugepage splits in the linear mapping would give
> admins the signal to narrow down the sluggishness caused by TLB
> miss/reload.
>
> One of the many lasting (as we don't coalesce back) sources for huge page
> splits is tracing as the granular page attribute/permission changes would
> force the kernel to split code segments mapped to huge pages to smaller
> ones thereby increasing the probability of TLB miss/reload even after
> tracing has been stopped.
>
> The split event information will be displayed at the bottom of
> /proc/meminfo
> ....
> DirectMap4k: 3505112 kB
> DirectMap2M: 19464192 kB
> DirectMap1G: 12582912 kB
> DirectMap2MSplits: 1705
> DirectMap1GSplits: 20
This seems much more like something we'd want in /proc/vmstat or as a
tracepoint than meminfo. A tracepoint would be especially nice because
the trace buffer could actually be examined if an admin finds an
excessive number of these.
next parent reply other threads:[~2021-01-25 20:16 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <BYAPR01MB40856478D5BE74CB6A7D5578CFBD9@BYAPR01MB4085.prod.exchangelabs.com>
2021-01-25 20:15 ` Dave Hansen [this message]
2021-01-25 20:32 ` [PATCH] x86/mm: Tracking linear mapping split events since boot Tejun Heo
2021-01-26 0:47 ` Dave Hansen
2021-01-26 0:53 ` Tejun Heo
2021-01-26 1:04 ` Dave Hansen
2021-01-26 1:17 ` Tejun Heo
2021-01-27 17:51 ` [PATCH V2] x86/mm: Tracking linear mapping split events Saravanan D
2021-01-27 21:03 ` Tejun Heo
2021-01-27 21:32 ` Dave Hansen
2021-01-27 21:36 ` Tejun Heo
2021-01-27 21:42 ` Saravanan D
2021-01-27 22:50 ` [PATCH V3] " Saravanan D
2021-01-27 23:00 ` Randy Dunlap
2021-01-27 23:56 ` Saravanan D
2021-01-27 23:41 ` Dave Hansen
2021-01-28 0:15 ` Saravanan D
2021-01-28 4:35 ` [PATCH V4] " Saravanan D
2021-01-28 4:51 ` Matthew Wilcox
[not found] ` <20210128104934.2916679-1-saravanand@fb.com>
2021-01-28 15:04 ` [PATCH V5] " Matthew Wilcox
2021-01-28 19:49 ` Saravanan D
2021-01-28 16:33 ` Zi Yan
2021-01-28 16:41 ` Dave Hansen
2021-01-28 16:56 ` Zi Yan
2021-01-28 16:59 ` Song Liu
[not found] ` <3aec2d10-f4c3-d07a-356f-6f1001679181@intel.com>
2021-01-28 21:20 ` Saravanan D
[not found] ` <20210128233430.1460964-1-saravanand@fb.com>
2021-01-28 23:41 ` [PATCH V6] " Tejun Heo
2021-01-29 19:27 ` Johannes Weiner
2021-02-08 23:17 ` Saravanan D
2021-02-08 23:30 ` Dave Hansen
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