Date: Sat, 7 Sep 2019 10:50:34 -0400 From: Mark Johnston <markj@freebsd.org> To: Slawa Olhovchenkov <slw@zxy.spb.ru> Cc: Andriy Gapon <avg@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r351673 - in head: lib/libmemstat share/man/man9 sys/cddl/compat/opensolaris/kern sys/kern sys/vm Message-ID: <20190907145034.GB6523@spy> In-Reply-To: <20190904144524.GD3953@zxy.spb.ru> References: <201909012222.x81MMh0F022462@repo.freebsd.org> <79c74018-1329-ee69-3480-e2f99821fa93@FreeBSD.org> <20190903161427.GA38096@zxy.spb.ru> <20190903220106.GB26733@raichu> <20190904144524.GD3953@zxy.spb.ru>
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On Wed, Sep 04, 2019 at 05:45:24PM +0300, Slawa Olhovchenkov wrote:
> On Tue, Sep 03, 2019 at 06:01:06PM -0400, Mark Johnston wrote:
> > > Mostly problem I am see at this
> > > work -- very slowly vm_page_free(). May be currenly this is more
> > > speedy...
> >
> > How did you determine this?
>
> This is you guess:
So was the guess correct? If so, IMO the real solution is to avoid kmem_*
for data buffers and use ABD instead.
> ======
> > while ((slab = SLIST_FIRST(&freeslabs)) != NULL) {
> > SLIST_REMOVE(&freeslabs, slab, uma_slab, us_hlink);
> > keg_free_slab(keg, slab, keg->uk_ipers);
> > }
> > 2019 Feb 2 19:49:54.800524364 zio_data_buf_1048576 1032605 cache_reclaim limit 100 dom 0 nitems 1672 imin 298
> > 2019 Feb 2 19:49:54.800524364 zio_data_buf_1048576 1033736 cache_reclaim recla 149 dom 0 nitems 1672 imin 298
> > 2019 Feb 2 19:49:54.802524468 zio_data_buf_1048576 3119710 cache_reclaim limit 100 dom 1 nitems 1 imin 0
> > 2019 Feb 2 19:49:54.802524468 zio_data_buf_1048576 3127550 keg_drain2
> > 2019 Feb 2 19:49:54.803524487 zio_data_buf_1048576 4444219 keg_drain3
> > 2019 Feb 2 19:49:54.838524634 zio_data_buf_1048576 39553705 keg_drain4
> > 2019 Feb 2 19:49:54.838524634 zio_data_buf_1048576 39565323 zone_reclaim:return
> >
> > 35109.486 ms for last loop, 149 items to freed.
>
> 35ms to free 149MB (38144 4KB pages), so roughly 1us per page. That
> does seem like a lot, but freeing a page (vm_page_free(m)) is much
> more expensive than freeing an item to UMA (i.e., uma_zfree()).
> Most of that time will be spent in _kmem_unback().
> ======
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