search for: preadv

On Thu, Nov 16, 2017 at 02:47:46PM +0000, Stefan Hajnoczi wrote: > The threads you observed are the thread pool that performs > preadv(2)/pwritev(2) syscalls. The Linux AIO API could be used instead > and does not use threads for read and write operations. I guess if I used AIO then I wouldn't get any parallelism at all since Linux doesn't block on local file access (at least, it never used to)? > Interesting. Di...

On Thu, Nov 16, 2017 at 3:10 PM, Richard W.M. Jones <rjones@redhat.com> wrote: > On Thu, Nov 16, 2017 at 02:47:46PM +0000, Stefan Hajnoczi wrote: >> The threads you observed are the thread pool that performs >> preadv(2)/pwritev(2) syscalls. The Linux AIO API could be used instead >> and does not use threads for read and write operations. > > I guess if I used AIO then I wouldn't get any parallelism at all since > Linux doesn't block on local file access (at least, it never used to)? Eve...

[CC to qemu-devel since I'm obviously doing something wrong here, I'm just not sure what.] I was getting ready to add multiple threads to ‘qemu-img convert’ (the longest part of v2v conversions) when I noticed that it had them already! (To be fair this was only added in February this year so no wonder we didn't notice.) To enable parallel convert we would need to use the ‘qemu-img

..., Nov 16, 2017 at 05:30:48PM +0000, Stefan Hajnoczi wrote: > On Thu, Nov 16, 2017 at 3:10 PM, Richard W.M. Jones <rjones@redhat.com> wrote: > > Both local filesystems, but on different SATA devices. > > Okay. I'm curious what the strace -f output looks like (only the > preadv(2)/pwritev(2) syscalls are interesting at the moment). Here's the full strace from one run: http://oirase.annexia.org/tmp/strace.xz The command is (with the output.qcow2 file created in a previous run): $ strace -o /tmp/strace -f -s 1024 qemu-img convert -f raw fedora-27.img -O qcow2 /v...

...writes to the destination) and > ‘qemu-img convert -m <#num-coroutines>’ option to select the > parallelism (defaults to 8). The documentation refers to coroutines > but I verified from strace that it is using real threads. The threads you observed are the thread pool that performs preadv(2)/pwritev(2) syscalls. The Linux AIO API could be used instead and does not use threads for read and write operations. So these threads are just an implementation detail. The caller doing the reads and writes is not multi-threaded but a number of coroutines executing in a single thread. The qe...

...tion) and >> ‘qemu-img convert -m <#num-coroutines>’ option to select the >> parallelism (defaults to 8). The documentation refers to coroutines >> but I verified from strace that it is using real threads. > The threads you observed are the thread pool that performs > preadv(2)/pwritev(2) syscalls. The Linux AIO API could be used instead > and does not use threads for read and write operations. So these > threads are just an implementation detail. The caller doing the reads > and writes is not multi-threaded but a number of coroutines executing in > a si...

...protect SYSCALL FOUND: getpriority SYSCALL FOUND: rt_sigaction SYSCALL FOUND: timer_delete SYSCALL FOUND: munmap SYSCALL FOUND: mremap SYSCALL FOUND: shutdown SYSCALL FOUND: epoll_create1 SYSCALL FOUND: readlinkat SYSCALL FOUND: fchmodat SYSCALL FOUND: chroot SYSCALL FOUND: lgetxattr SYSCALL FOUND: preadv SYSCALL FOUND: getresgid SYSCALL FOUND: pselect6 SYSCALL FOUND: pciconfig_write SYSCALL FOUND: getsockname SYSCALL FOUND: eventfd SYSCALL FOUND: setitimer SYSCALL FOUND: sched_get_priority_max SYSCALL FOUND: getcpu SYSCALL FOUND: sendfile SYSCALL FOUND: pipe2 SYSCALL FOUND: acct SYSCALL FOUND: afs_...

On Tue, Aug 20, 2013 at 07:44:39AM +0200, leroy christophe wrote: > > > Find attached two patches I have in order to build klibc 2.0.2 > against kernel 3.8.13 > We had to introduce those patches when going from kernel 3.6 to kernel 3.7 > Hope it helps. > those patches are wrong and again very brittle. just use the way it is described in `make help': A) cd ~/src/linux