Date: Wed, 14 Oct 2009 13:16:29 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-stable@freebsd.org Subject: Re: Extreme console latency during disk IO (8.0-RC1, previous releases also affected according to others) Message-ID: <hb4bu5$p9d$1@ger.gmane.org> In-Reply-To: <alpine.BSF.2.00.0910131328400.34883@thebighonker.lerctr.org> References: <E316139E-FFCF-432F-8DCE-62B120C38E55@exscape.org> <CC16B639-7A75-4016-A8A8-5C59E9CD5E95@exscape.org> <hb1qs0$qjd$1@ger.gmane.org> <alpine.BSF.2.00.0910131406340.26071@fledge.watson.org> <9bbcef730910130633w150571a0k461fb4e67a51fb1d@mail.gmail.com> <B5BA3ACC-BC06-4042-8434-0D9395A0F478@freebsd.org> <hb23i7$opq$1@ger.gmane.org> <alpine.BSF.2.00.0910130957540.26159@thebighonker.lerctr.org> <9bbcef730910131057i71db846et1f0d4aeadef5e302@mail.gmail.com> <alpine.BSF.2.00.0910131328400.34883@thebighonker.lerctr.org>
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Larry Rosenman wrote: > On Tue, 13 Oct 2009, Ivan Voras wrote: >> As for what data is needed, it depends on what you can get - from this >> discussion thread it looks like it would be enough to verify that disk >> IO doesn't leave VM processes waiting (i.e. that disk IO doesn't >> interfere with CPU-bound or idle virtual machines). Though now when I >> think of it - doesn't Linux ATA driver poll IO in some funky way, >> expecting to get lower latency that way? >> > Have you looked at the information available via the performance tab(s) > in the > client pointing at the ESXi server? The 20 second time resolution I get in performance charts isn't nearly enough to diagnose something like this. I've now been running iostat in the virtual console (not ssh) during disk IO and I can't seem to get the characteristic "stutter" / pause behaviour so I think that it's very likely there is too much going on in the VM software to accurately conclude anything.
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