Date: Sat, 5 Jan 2008 05:26:47 +0200 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: Igor Mozolevsky <igor@hybrid-lab.co.uk> Cc: Dag-Erling Sm?rgrav <des@des.no>, freebsd-current@freebsd.org, Robert Watson <rwatson@freebsd.org>, Jason Evans <jasone@freebsd.org> Subject: Re: sbrk(2) broken Message-ID: <20080105032647.GA46843@kobe.laptop> In-Reply-To: <a2b6592c0801040318s9986f10u40cf725bc96304c6@mail.gmail.com> References: <477C82F0.5060809@freebsd.org> <863ateemw2.fsf@ds4.des.no> <20080104002002.L30578@fledge.watson.org> <a2b6592c0801040241l598ea9b7h57ad6889a1eccd3@mail.gmail.com> <86bq81c12d.fsf@ds4.des.no> <a2b6592c0801040318s9986f10u40cf725bc96304c6@mail.gmail.com>
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On 2008-01-04 11:18, Igor Mozolevsky <igor@hybrid-lab.co.uk> wrote: > On 04/01/2008, Dag-Erling Sm?rgrav <des@des.no> wrote: > > Of course, if you're afraid of memory overcommit and you know in advance > > how much memory you need, you can simply allocate a sufficient amount of > > address space at startup and touch it all. This way, you will either be > > killed right away, or be guaranteed to have sufficient memory for the > > rest of your (process) lifetime. Alternatively, do what Varnish does: > > create a large file, mmap it, and allocate everything you need from that > > area, so you have your own private swap space. Just make sure to > > actually allocate the disk space you need (by filling the file with > > zeroes, or at the minimum writing a zero to the file every sb.st_blksize > > bytes, preferably sequentially to avoid excessive fragmentation) > > Surely you can just fseek() on the file at the correct lenght? That would create a nicely sized 'hole' in the starting blocks. What Dag-Erling describes is the correct(TM) way of making sure that all blocks have been allocated from the backing store of the file.
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