Date: Wed, 14 Jan 2026 00:08:52 +0100 From: Oliver Pinter <oliver.pntr@gmail.com> To: Konstantin Belousov <kib@freebsd.org> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 457b940bfb6a - main - tuning.7: add more explanation about swap (over-)accounting Message-ID: <CAPjTQNGOVG=YLqKhrvwYjJg3_ZqD_v=ULUXA_4GBALrbstBB7A@mail.gmail.com> In-Reply-To: <696650ad.a11e.704a7e09@gitrepo.freebsd.org>
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[-- Attachment #1 --] Hi! Attached a small fix. On Tue, Jan 13, 2026 at 3:04 PM Konstantin Belousov <kib@freebsd.org> wrote: > > The branch main has been updated by kib: > > URL: https://cgit.FreeBSD.org/src/commit/?id=457b940bfb6a228af1281f357b627ecf1e26fea5 > > commit 457b940bfb6a228af1281f357b627ecf1e26fea5 > Author: Konstantin Belousov <kib@FreeBSD.org> > AuthorDate: 2026-01-12 03:54:58 +0000 > Commit: Konstantin Belousov <kib@FreeBSD.org> > CommitDate: 2026-01-13 14:03:14 +0000 > > tuning.7: add more explanation about swap (over-)accounting > > Sponsored by: The FreeBSD Foundation > MFC after: 1 week > Differential revision: https://reviews.freebsd.org/D54572 > --- > share/man/man7/tuning.7 | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/share/man/man7/tuning.7 b/share/man/man7/tuning.7 > index 44c427c4559d..a3709ce82b8c 100644 > --- a/share/man/man7/tuning.7 > +++ b/share/man/man7/tuning.7 > @@ -222,6 +222,21 @@ and > .Va vm.stats.vm.v_wire_count > sysctls, respectively). > .Pp > +Due to the architecture of the > +.Fx > +virtual memory subsystem, the use of copy on write (CoW) anonymous > +memory, e.g. on > +.Xr fork 2 , > +causes swap reservation for all three regions (VM objects), > +as in the original pre-fork mapping, and its copies in > +the parent and child, instead of only two. > +Eventually the subsystem tries to optimize the internal layout > +of the tracking for CoW and often removes (collapses) no longer > +needed backing objects, re-assigning its pages and swap > +reservations to the copies. > +Coolapsing frees the swap reserve, but it is not guaranteed > +to happen. > +.Pp > The > .Va kern.ipc.maxpipekva > loader tunable is used to set a hard limit on the > [-- Attachment #2 --] From 8217ebe6b06112967e0b6c82f7dcdb63879cdc4d Mon Sep 17 00:00:00 2001 From: Oliver Pinter <oliver.pntr+freebsd@gmail.com> Date: Wed, 14 Jan 2026 00:06:29 +0100 Subject: [PATCH] tuning.7: use the correct word for collapsing Fixes: 457b940bfb6a228af1281f357b627ecf1e26fea5 Signed-off-by: Oliver Pinter <oliver.pntr+freebsd@gmail.com> --- share/man/man7/tuning.7 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/share/man/man7/tuning.7 b/share/man/man7/tuning.7 index a3709ce82b8c..daf941da5de3 100644 --- a/share/man/man7/tuning.7 +++ b/share/man/man7/tuning.7 @@ -234,7 +234,7 @@ Eventually the subsystem tries to optimize the internal layout of the tracking for CoW and often removes (collapses) no longer needed backing objects, re-assigning its pages and swap reservations to the copies. -Coolapsing frees the swap reserve, but it is not guaranteed +Collapsing frees the swap reserve, but it is not guaranteed to happen. .Pp The -- 2.50.1 (Apple Git-155)home | help
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