control: tag -1 + moreinfo On 2016-02-15 12:56, Antti Salmela wrote: > Package: libc6 > Severity: normal > > Dear Maintainer, > > something has changed in libc6 between jessie and stretch which has a lead > to a performance regression. I noticed this first with ssh file transfers, but > tested using same version of iperf3 and kernel 4.3.0-1-amd64 on both hosts. > Both hosts are running as Xen guests on same otherwise completely idle > hardware. Running under Xen is probably needed to reproduce, I can't reproduce > regression on similar bare hardware.
What makes you think this is a libc6 issue? Could you please at least try to do the same test with a jessie machine with only libc6 and related packages updated to stretch. > $ iperf3 -c stretch [snip] > # > # Overhead Command Shared Object Symbol > > # ........ ....... ................. > .......................................... > # > 34.78% iperf3 [kernel.kallsyms] [k] xen_hypercall_xen_version The culprit seems to be the above line, which is not related to glibc? > 13.04% iperf3 libc-2.21.so [.] random_r > > 4.35% iperf3 [kernel.kallsyms] [k] __pollwait > > 4.35% iperf3 [kernel.kallsyms] [k] copy_page_to_iter > > 4.35% iperf3 [kernel.kallsyms] [k] dnotify_flush > > 4.35% iperf3 [kernel.kallsyms] [k] fsnotify > > 4.35% iperf3 [kernel.kallsyms] [k] inet_twsk_alloc > > 4.35% iperf3 [kernel.kallsyms] [k] release_sock > > 4.35% iperf3 [kernel.kallsyms] [k] sys_read > > 4.35% iperf3 [kernel.kallsyms] [k] tcp_recvmsg > > 4.35% iperf3 [kernel.kallsyms] [k] xen_hypercall_mmu_update > > 4.35% iperf3 [kernel.kallsyms] [k] xennet_alloc_rx_buffers > > 4.35% iperf3 libc-2.21.so [.] random > > 4.35% iperf3 libc-2.21.so [.] read > [snip] > $ iperf3 -c jessie [snip] > # > # Overhead Command Shared Object Symbol > # ........ ....... ................. ............................. > # > 15.79% iperf3 libc-2.19.so [.] random > 15.79% iperf3 libc-2.19.so [.] random_r > 10.53% iperf3 [kernel.kallsyms] [k] unmap_single_vma > 10.53% iperf3 [kernel.kallsyms] [k] xen_hypercall_mmu_update > 10.53% iperf3 [kernel.kallsyms] [k] xen_hypercall_xen_version On jessie it was using 3 times less CPU. > 5.26% iperf3 [kernel.kallsyms] [k] copy_user_generic_string > 5.26% iperf3 [kernel.kallsyms] [k] fsnotify > 5.26% iperf3 [kernel.kallsyms] [k] get_pfnblock_flags_mask > 5.26% iperf3 [kernel.kallsyms] [k] kmem_cache_free > 5.26% iperf3 [kernel.kallsyms] [k] sys_read > 5.26% iperf3 [kernel.kallsyms] [k] sys_select > 5.26% iperf3 [kernel.kallsyms] [k] tcp_poll -- Aurelien Jarno GPG: 4096R/1DDD8C9B [email protected] http://www.aurel32.net
