Date: Thu, 15 Nov 2012 11:32:18 -0600 From: Alan Cox <alc@rice.edu> To: Konstantin Belousov <kostikbel@gmail.com> Cc: alc@freebsd.org, pho@freebsd.org, Sushanth Rai <sushanth_rai@yahoo.com>, StevenSears <Steven.Sears@netapp.com>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: Memory reserves or lack thereof Message-ID: <50A52722.7050100@rice.edu> In-Reply-To: <20121113115445.GK73505@kib.kiev.ua> References: <20121112133638.GZ73505@kib.kiev.ua> <1352755682.93266.YahooMailClassic@web181701.mail.ne1.yahoo.com> <20121112214808.GH73505@kib.kiev.ua> <50A181C9.7030209@rice.edu> <20121113115445.GK73505@kib.kiev.ua>
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On 11/13/2012 05:54, Konstantin Belousov wrote: > On Mon, Nov 12, 2012 at 05:10:01PM -0600, Alan Cox wrote: >> On 11/12/2012 3:48 PM, Konstantin Belousov wrote: >>> On Mon, Nov 12, 2012 at 01:28:02PM -0800, Sushanth Rai wrote: >>>> This patch still doesn't address the issue of M_NOWAIT calls driving >>>> the memory the all the way down to 2 pages, right ? It would be nice to >>>> have M_NOWAIT just do non-sleep version of M_WAITOK and M_USE_RESERVE >>>> flag to dig deep. >>> This is out of scope of the change. But it is required for any further >>> adjustements. >> I would suggest a somewhat different response: >> >> The patch does make M_NOWAIT into a "non-sleep version of M_WAITOK" and >> does reintroduce M_USE_RESERVE as a way to specify "dig deep". >> >> Currently, both M_NOWAIT and M_WAITOK can drive the cache/free memory >> down to two pages. The effect of the patch is to stop M_NOWAIT at two >> pages rather than allowing it to continue to zero pages. >> >> When you say, "This is out of scope ...", I believe that you are >> referring to changing two pages into something larger. I agree that >> this is out of scope for the current change. > I referred exactly to the difference between M_USE_RESERVE set or not. > IMO this is what was asked by the question author. So yes, my mean of > the 'out of scope' is about tweaking the 'two pages reserve' in some > way. Since M_USE_RESERVE is no longer deprecated in HEAD, here is my proposed man page update to malloc(9): Index: share/man/man9/malloc.9 =================================================================== --- share/man/man9/malloc.9 (revision 243091) +++ share/man/man9/malloc.9 (working copy) @@ -29,7 +29,7 @@ .\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $ .\" $FreeBSD$ .\" -.Dd January 28, 2012 +.Dd November 15, 2012 .Dt MALLOC 9 .Os .Sh NAME @@ -153,13 +153,12 @@ if .Dv M_WAITOK is specified. .It Dv M_USE_RESERVE -Indicates that the system can dig into its reserve in order to obtain the -requested memory. -This option used to be called -.Dv M_KERNEL -but has been renamed to something more obvious. -This option has been deprecated and is slowly being removed from the kernel, -and so should not be used with any new programming. +Indicates that the system can use its reserve of memory to satisfy the +request. +This option should only be used in combination with +.Dv M_NOWAIT +when an allocation failure cannot be tolerated by the caller without +catastrophic effects on the system. .El .Pp Exactly one of either
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