Re: [Qemu-devel] Serious regression of 9p read performance, huge amount of openat syscalls on plain file descriptors

2012-01-13 Thread Lutz Vieweg
The regression does not exist in the way that I suspected - it's just that the default for 9p mount option msize=4096 causes the bad performance when reading large files on the guest. I was mislead because... a) mount -o remount,msize=...,... seems to work (with mount reporting the changed

[Qemu-devel] Serious regression of 9p read performance, huge amount of openat syscalls on plain file descriptors

2012-01-12 Thread Lutz Vieweg
Hi all, I have been using 9p mounts on guests for quite some time, and enjoyed their nice performance. But not anymore: I noticed that just dd-ing large plain files to /dev/zero on the guest system became very slow, even if the data is completely in the cache of the host. The rate maxes at ~