From: Michal Hocko <firstname.lastname@example.org> To: Daniel Colascione <email@example.com> Cc: Qian Cai <firstname.lastname@example.org>, Tim Murray <email@example.com>, Suren Baghdasaryan <firstname.lastname@example.org>, email@example.com, linux-kernel <firstname.lastname@example.org>, linux-mm <email@example.com> Subject: Re: [PATCH] Make SPLIT_RSS_COUNTING configurable Date: Fri, 4 Oct 2019 14:33:49 +0200 [thread overview] Message-ID: <20191004123349.GB10845@dhcp22.suse.cz> (raw) In-Reply-To: <CAKOZuesKY_=qkSXfmDO_1ALaqQtU0kz5Z+fBh05c8BR7oCDxKw@mail.gmail.com> On Wed 02-10-19 19:08:16, Daniel Colascione wrote: > On Wed, Oct 2, 2019 at 6:56 PM Qian Cai <firstname.lastname@example.org> wrote: > > > On Oct 2, 2019, at 4:29 PM, Daniel Colascione <email@example.com> wrote: > > > > > > Adding the correct linux-mm address. > > > > > > > > >> +config SPLIT_RSS_COUNTING > > >> + bool "Per-thread mm counter caching" > > >> + depends on MMU > > >> + default y if NR_CPUS >= SPLIT_PTLOCK_CPUS > > >> + help > > >> + Cache mm counter updates in thread structures and > > >> + flush them to visible per-process statistics in batches. > > >> + Say Y here to slightly reduce cache contention in processes > > >> + with many threads at the expense of decreasing the accuracy > > >> + of memory statistics in /proc. > > >> + > > >> endmenu > > > > All those vague words are going to make developers almost impossible to decide the right selection here. It sounds like we should kill SPLIT_RSS_COUNTING at all to simplify the code as the benefit is so small vs the side-effect? > > Killing SPLIT_RSS_COUNTING would be my first choice; IME, on mobile > and a basic desktop, it doesn't make a difference. I figured making it > a knob would help allay concerns about the performance impact in more > extreme configurations. I do agree with Qian. Either it is really helpful (is it? probably on the number of cpus) and it should be auto-enabled or it should be dropped altogether. You cannot really expect people know how to enable this without a deep understanding of the MM internals. Not to mention all those users using distro kernels/configs. A config option sounds like a bad way forward. -- Michal Hocko SUSE Labs
next prev parent reply other threads:[~2019-10-04 12:33 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-02 20:24 Daniel Colascione 2019-10-02 20:28 ` Daniel Colascione 2019-10-03 1:56 ` Qian Cai 2019-10-03 2:08 ` Daniel Colascione 2019-10-04 12:33 ` Michal Hocko [this message] 2019-10-04 13:26 ` Kirill A. Shutemov 2019-10-04 13:45 ` Daniel Colascione 2019-10-04 14:43 ` Michal Hocko 2019-10-07 0:11 ` Kirill A. Shutemov
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20191004123349.GB10845@dhcp22.suse.cz \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --subject='Re: [PATCH] Make SPLIT_RSS_COUNTING configurable' \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).