Messages in this thread | | | Date | Wed, 23 Jul 2014 12:57:51 +0200 | From | Pavel Machek <> | Subject | Re: [PATCH 0/6 v2] PM / Hibernate: Memory bitmap scalability improvements |
| |
On Tue 2014-07-22 14:10:22, Joerg Roedel wrote: > On Tue, Jul 22, 2014 at 12:58:12PM +0200, Pavel Machek wrote: > > On Tue 2014-07-22 12:34:44, Joerg Roedel wrote: > > > On Tue, Jul 22, 2014 at 02:41:29AM +0200, Rafael J. Wysocki wrote: > > > > It looks like some specific need motivated the Joerg's work, however, > > > > so let's just not dismiss the use case lightly without knowing it. > > > > > > The motivation was to optimize the data structures for machines with > > > large amounts of RAM without penalizing average machines. On a 12TB > > > machine you are close to 100000 pages just for one bitmap. Scanning > > > through that linearly to find a given bit just doesnt scale anymore in > > > this case. > > > > Can you produce backtrace where 12TB machine spends time during boot > > with resume= parameter but no suspend image? > > > > AFAICT swsusp_check() does not play with bitmaps. > > I can ask for a backtrace, I currently don't have one. But I have > perf-data for this case. It also shows that it spends most of its time > with bitmap operations: > > ~# time perf record /usr/sbin/resume $sdev > resume: libgcrypt version: 1.5.0 > [ perf record: Woken up 12 times to write data ] > [ perf record: Captured and wrote 2.882 MB perf.data (~125898 samples) ]
Aha, but that's the userland code... suspend package, resume.c:
dev = open(snapshot_dev_name, O_WRONLY); if (dev < 0) { error = ENOENT; goto Free; }
resume_dev = open_resume_dev(resume_dev_name, &swsusp_header); if (resume_dev == -ENOMEDIUM) { error = 0; goto Close; } else if (resume_dev < 0) { error = -resume_dev; goto Close; }
What your probably want to do is open_resume_dev first, and only open(snapshot_dev_name...) if it finds correct signature. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
| |