Date: Wed, 9 Aug 2017 22:23:50 +0530 From: Gautam <list@execve.net> To: freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Re: Freebsd 11.0 - system freeze on intensive I/O Message-ID: <CAD9pFYCxBO18GmRE6=-i==j3puJqgQ7bvPk7dmP%2B=T2hgbaAcw@mail.gmail.com> In-Reply-To: <B0B159BA-3C4A-4A5C-B3EB-CBF2CF251274@dsl-only.net> References: <CAD9pFYAAy8jKcABNTun-Y3knrbUreQ7q1-CCj=323HgLMC5e6g@mail.gmail.com> <598ADB65.8060701@grosbein.net> <CALH631mEEcUwceh1UYhpF664SoEA4P%2BU87VEhrY-vnZrrQ%2Bw8g@mail.gmail.com> <B0B159BA-3C4A-4A5C-B3EB-CBF2CF251274@dsl-only.net>
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Hi, On Wed, Aug 9, 2017 at 7:43 PM, Mark Millard <markmi@dsl-only.net> wrote: > > Swap files on ZFS are also known to have the problem. > > Quoting bugzilla 206048's comment #7 (which is quoting an older > list message): > > On 2017-Feb-13, at 7:20 PM, Konstantin Belousov <kostikbel at gmail.com> > wrote > on the freebsd-arm list: > > . . . > > swapfile write requires the write request to come through the filesystem > write path, which might require the filesystem to allocate more memory > and read some data. E.g. it is known that any ZFS write request > allocates memory, and that write request on large UFS file might require > allocating and reading an indirect block buffer to find the block number > of the written block, if the indirect block was not yet read. > > As result, swapfile swapping is more prone to the trivial and unavoidable > deadlocks where the pagedaemon thread, which produces free memory, needs > more free memory to make a progress. Swap write on the raw partition ove= r > simple partitioning scheme directly over HBA are usually safe, while e.g. > zfs over geli over umass is the worst construction. > > =E2=80=8BFirstly, thanks all for the responses. I just want to comment, that when I tested it there was absolutely no need for any swap usage. I tried the test on a laptop with 8GB RAM and did it from the console mode. But it does seem that there might be some request (read/write) to swap which =E2=80=8Bcauses a lock up to the system.=E2=80=8B =E2=80=8BThanks, Gautam =E2=80=8B
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