Date: Sun, 11 Nov 2012 18:02:36 -0800 From: Adrian Chadd <adrian@freebsd.org> To: alc@freebsd.org Cc: Konstantin Belousov <kostikbel@gmail.com>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, "Sears, Steven" <Steven.Sears@netapp.com> Subject: Re: Memory reserves or lack thereof Message-ID: <CAJ-Vmo=tk_yiukE_uZzDAgh6Q1RP=5Jz1G0heq%2BcANJ1di8Wzg@mail.gmail.com> In-Reply-To: <CAJUyCcOKHH3TO6qaK9V7UY2HW%2Bp6T74DUUdmbSi4eeGyofrTdQ@mail.gmail.com> References: <A6DE036C6A90C949A25CE89E844237FB2086970A@SACEXCMBX01-PRD.hq.netapp.com> <20121110132019.GP73505@kib.kiev.ua> <CAJUyCcOKHH3TO6qaK9V7UY2HW%2Bp6T74DUUdmbSi4eeGyofrTdQ@mail.gmail.com>
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On 11 November 2012 13:40, Alan Cox <alan.l.cox@gmail.com> wrote: > > Agreed. Once upon time, before SMPng, M_NOWAIT was rarely used. It was > well understand that it should only be used by interrupt handlers. > > The trouble is that M_NOWAIT conflates two orthogonal things. The obvious > being that the allocation shouldn't sleep. The other being how far we're > willing to deplete the cache/free page queues. > > When fine-grained locking got sprinkled throughout the kernel, we all to > often found ourselves wanting to do allocations without the possibility of > blocking. So, M_NOWAIT became commonplace, where it wasn't before. Well, what's the current set of best practices for allocating mbufs? I don't mind going through ath(4) and net80211(4), looking to make it behave better with mbuf allocations. There's 49 M_NOWAIT's in net80211 and 10 in ath(4). I wonder how many of them are synonyms with "don't fail allocating", too. Hm. Adrian
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