On Mon, Dec 04, 2017 at 08:03:22PM +0800, Yang Zhong wrote: > On Fri, Dec 01, 2017 at 01:52:49PM +0100, Paolo Bonzini wrote: > > On 01/12/2017 11:56, Yang Zhong wrote: > > > This issue should be caused by much times of system call by > > > malloc_trim(), > > > Shannon's test script include 60 scsi disks and 31 ioh3420 devices. We > > > need > > > trade-off between VM perforamance and memory optimization. Whether > > > below > > > method is suitable? > > > > > > int num=1; > > > ...... > > > > > > #if defined(CONFIG_MALLOC_TRIM) > > > if(!(num++%5)) > > > { > > > malloc_trim(4 * 1024 * 1024); > > > } > > > #endif > > > > > > Any comments are welcome! Thanks a lot! > > > > Indeed something like this will do, perhaps only trim once per second? > > > Hello Paolo, > > Thanks for comments! > If we do trim once per second, maybe the frequency is a little high, what'e > more, we need maintain one timer to call this, this also cost cpu resource. > > I added the log and did the test here with my test qemu command, when VM > bootup, > which did more than 600 times free operations and 9 times memory trim in > rcu > thread. If i use our ClearContainer qemu command, the memory trim will down > to 6 times. As for Shannon's test command, the malloc trim number will > abosultly > increse. > > In my above method, the trim is only executed in the multiple of 5, which > will > reduce trim times and do not heavily impact VM bootup performance. > > I also want to use synchronize_rcu() and free() to replace call_rcu(), but > this > method serialize to malloc() and free(), which will reduce VM performance. > > The ultimate aim is to reduce trim system call during the VM bootup and > running. > It's appreciated that if you have better suggestions.
Does configuring QEMU to use tcmalloc or jemalloc instead of glibc's malloc give you the performance & menmory usage that you require? If so, it might not be worth bothering to hack around problems in glibc's malloc at all. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|