Date: Sat, 7 Aug 2010 19:58:15 +0200 From: Ivan Voras <ivoras@freebsd.org> To: Joshua Boyd <boydjd@jbip.net> Cc: freebsd-stable@freebsd.org Subject: Re: 8-STABLE Slow Write Speeds on ESXI 4.0 Message-ID: <AANLkTimMA6OQKt-d6ecM=GmG2ciBTis-nHNovEwvjCB-@mail.gmail.com> In-Reply-To: <AANLkTik%2BS2fe-sS242OXQprsEA4Oh4t6-CvBCuBCASz7@mail.gmail.com> References: <AANLkTi=FNZ%2B=4yMPJBu%2BucGJiHqwMwQvoGcgqB%2BtPJF2@mail.gmail.com> <i3jhn0$ovp$1@dough.gmane.org> <AANLkTik%2BS2fe-sS242OXQprsEA4Oh4t6-CvBCuBCASz7@mail.gmail.com>
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On 7 August 2010 19:03, Joshua Boyd <boydjd@jbip.net> wrote: > On Sat, Aug 7, 2010 at 7:57 AM, Ivan Voras <ivoras@freebsd.org> wrote: >> It's unlikely they will help, but try: >> >> vfs.read_max=32 >> >> for read speeds (but test using the UFS file system, not as a raw device >> like above), and: >> >> vfs.hirunningspace=8388608 >> vfs.lorunningspace=4194304 >> >> for writes. Again, it's unlikely but I'm interested in results you >> achieve. >> > > This is interesting. Write speeds went up to 40MBish. Still slow, but 4x > faster than before. > [root@git ~]# dd if=/dev/zero of=/var/testfile bs=1M count=250 > 250+0 records in > 250+0 records out > 262144000 bytes transferred in 6.185955 secs (42377288 bytes/sec) > [root@git ~]# dd if=/var/testfile of=/dev/null > 512000+0 records in > 512000+0 records out > 262144000 bytes transferred in 0.811397 secs (323077424 bytes/sec) > So read speeds are up to what they should be, but write speeds are still > significantly below what they should be. Well, you *could* double the size of "runningspace" tunables and try that :) Basically, in tuning these two settings we are cheating: increasing read-ahead (read_max) and write in-flight buffering (runningspace) in order to offload as much IO to the controller (in this case vmware) as soon as possible, so to reschedule horrible IO-caused context switches vmware has. It will help sequential performance, but nothing can help random IOs.
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