Date: Sat, 3 Jul 2021 08:54:20 +0200 From: Gary Jennejohn <gljennjohn@gmail.com> To: Vitaliy Gusev <gusev.vitaliy@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: madvise(MADV_FREE) doesn't work in some cases? Message-ID: <20210703065420.6dbafb5f@ernst.home> In-Reply-To: <D5749BDF-36B5-4AE9-A75F-2A702DF71F8C@gmail.com> References: <D5749BDF-36B5-4AE9-A75F-2A702DF71F8C@gmail.com>
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On Sat, 3 Jul 2021 02:56:40 +0300 Vitaliy Gusev <gusev.vitaliy@gmail.com> wrote: > Hi, > > I came across not expected behaviour with madvise() in FreeBSD. > > Attached test program mmapfork does: mmap, fork, touch memory and then madvise(MADV_FREE). > > Expected behaviour - one process can allocate memory (lazy allocation) while system is freeing previously allocated memory for a second process. > > Current behaviour - system kills one process with message in dmesg: > > pid 31314 (mmapfork), jid 0, uid 1001, was killed: out of swap space > > Running this test in Linux or illumos shows expected behaviour with a little difference in illumos - it frees memory almost immediately, w/o needs lack of memory in a system. > > If use MADV_NOTNEED - no changes. > > If modify program and do not do fork(), but run two instances - that shows expected behaviour. > > To reproduce just disable swap, and run program with argument as 1/2 RAM on a system. For instance, command below will try run and use ~ 2GB area twice. > > [vetal@bsdev ~]$ ./mmapfork 2000 > > Testing program is attached. > > Note, during testing I disabled swap on all systems: Linux, illumos and FreeBSD. > > Does it mean madvise() doesn't work well in FreeBSD or test does something wrong? > The FreeBSD mail server apparently removed the attachment. So either provide it in-line or put it on some pubic file server and add a link to it. -- Gary Jennejohn
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