Date: Wed, 17 Aug 2022 15:09:45 -0700 From: Gleb Smirnoff <glebius@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 81a34d374ed6 - main - protosw: retire pr_drain and use EVENTHANDLER(9) directly Message-ID: <Yv1nKXi77zMU89Aw@FreeBSD.org> In-Reply-To: <Yv1hOLxDo8rDMzfR@kib.kiev.ua> References: <202208171852.27HIqL67013112@gitrepo.freebsd.org> <Yv1hOLxDo8rDMzfR@kib.kiev.ua>
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On Thu, Aug 18, 2022 at 12:44:24AM +0300, Konstantin Belousov wrote: K> > protosw: retire pr_drain and use EVENTHANDLER(9) directly K> > K> > The method was called for two different conditions: 1) the VM layer is K> > low on pages or 2) one of UMA zones of mbuf allocator exhausted. K> > This change 2) into a new event handler, but all affected network K> > subsystems modified to subscribe to both, so this change shall not K> > bring functional changes under different low memory situations. K> > K> > There were three subsystems still using pr_drain: TCP, SCTP and frag6. K> > The latter had its protosw entry for the only reason to register its K> > pr_drain method. K> > K> > Reviewed by: tuexen, melifaro K> > Differential revision: https://reviews.freebsd.org/D36164 K> ... K> K> > diff --git a/sys/vm/vm_pageout.h b/sys/vm/vm_pageout.h K> > index 82ba3c81ef1b..63d31dc1d135 100644 K> > --- a/sys/vm/vm_pageout.h K> > +++ b/sys/vm/vm_pageout.h K> > @@ -87,6 +87,7 @@ extern int vm_pageout_page_count; K> > */ K> > #define VM_LOW_KMEM 0x01 K> > #define VM_LOW_PAGES 0x02 K> > +#define VM_LOW_MBUFS 0x04 K> K> This is very weird, to put it mildly. As said in the commit message the old code called the pr_drain for two very different events and new code just preserves old behavior. I didn't create the weirdness, I exposed it :) I'm open to redesigning this. This probably needs to be done separately for every protocol and tested in real life conditions that indeed trigger these events. -- Gleb Smirnoff
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