From: Bart Schaefer <schaefer@brasslantern.com>
To: zsh-workers@zsh.org
Subject: Re: Slowdown around 5.0.5-dev-0
Date: Sat, 10 Oct 2015 10:58:49 -0700 [thread overview]
Message-ID: <151010105849.ZM10144@torch.brasslantern.com> (raw)
In-Reply-To: <CAKc7PVDAS+yud1ChCsAMMKqNF=vEPcbN51czm56veKcS3WZxyg@mail.gmail.com>
On Oct 10, 12:54pm, Sebastian Gniazdowski wrote:
} Subject: Slowdown around 5.0.5-dev-0
}
} I was testing my scripts and saw that on 5.0.2 having 89k-elements
} long is much faster than on 5.1.1-dev-0. I ran git bisect and found
} the commit:
}
} 2014-01-18 23f98c3 32285: restart the fheap search in freeheap if the
} current fheap arena is about to be discarded; fixes crash
If you look back through the zsh-workers articles, you'll find that
the performance was even worse prior to workers/29175; there was a
huge gain in performance from that patch, but it introduced a crash
bug, so we had to give back some of the performance in workers/32285
to prevent the crash from happening.
Read the large comment in freeheap() for a description of what is
going on there, note particularly the paragraph ending "performance
goes to hell."
I fear a signficant rewrite of the heap-allocation code would be needed
to both avoid the crash and improve the performance. The current code
was designed with the expectation that zhalloc() would be a much more
common operation than freeheap(), but there are circumstances in which
the latter happens a lot.
It's possible that we could figure out a way to skip the scan that
updates all the h->used values in freeheap(), and pay the price on the
next zhalloc() instead.
I think (but am not 100% sure) that the pathological case happens when
the heap is already maximally filled, so a new arena is always added
to the end of the chain and then dropped again on each alloc/free.
On the other hand the shell really isn't intended to be manipulating
arrays of containing tens of thousands of elements.
next prev parent reply other threads:[~2015-10-10 17:58 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-10 10:54 Sebastian Gniazdowski
2015-10-10 17:58 ` Bart Schaefer [this message]
2015-10-10 18:11 ` Sebastian Gniazdowski
2015-10-10 18:32 ` Sebastian Gniazdowski
2015-10-11 0:06 ` Bart Schaefer
2015-10-11 6:20 ` Bart Schaefer
2015-10-11 8:39 ` Sebastian Gniazdowski
2015-10-11 16:17 ` Bart Schaefer
2015-10-11 16:48 ` Sebastian Gniazdowski
2015-10-11 17:31 ` Bart Schaefer
2015-10-11 18:05 ` Sebastian Gniazdowski
2015-10-11 21:22 ` Bart Schaefer
2015-10-12 8:21 ` Sebastian Gniazdowski
2015-10-12 14:01 ` Bart Schaefer
2015-10-12 16:50 ` Sebastian Gniazdowski
2015-10-13 0:33 ` Bart Schaefer
2015-10-13 8:21 ` Sebastian Gniazdowski
2015-10-13 15:52 ` Bart Schaefer
2015-10-14 6:50 ` Sebastian Gniazdowski
2015-10-14 13:27 ` Peter Stephenson
2015-10-14 16:25 ` Bart Schaefer
2015-10-14 16:50 ` Bart Schaefer
2015-10-15 4:32 ` Bart Schaefer
2015-10-15 13:03 ` Sebastian Gniazdowski
2015-10-16 0:35 ` Bart Schaefer
2015-10-17 9:12 ` Sebastian Gniazdowski
2015-10-17 9:24 ` Sebastian Gniazdowski
2015-10-18 16:19 ` Bart Schaefer
2015-10-18 20:40 ` Sebastian Gniazdowski
2015-10-18 21:07 ` Bart Schaefer
2015-10-18 21:31 ` Sebastian Gniazdowski
2015-10-19 17:21 ` Bart Schaefer
2015-10-22 12:49 ` Sebastian Gniazdowski
2015-10-22 15:00 ` Bart Schaefer
2015-10-22 16:28 ` Sebastian Gniazdowski
2015-10-22 16:33 ` Sebastian Gniazdowski
2015-10-23 15:40 ` Sebastian Gniazdowski
2015-10-23 15:57 ` Sebastian Gniazdowski
2015-10-23 19:26 ` Bart Schaefer
2015-10-23 23:50 ` Bart Schaefer
2015-10-24 6:09 ` Sebastian Gniazdowski
2015-10-24 7:37 ` Sebastian Gniazdowski
2015-10-24 8:04 ` Sebastian Gniazdowski
2015-10-24 19:39 ` Bart Schaefer
2015-10-25 7:35 ` Sebastian Gniazdowski
2015-10-25 17:23 ` Bart Schaefer
2015-10-25 20:56 ` Sebastian Gniazdowski
2015-10-26 0:49 ` Bart Schaefer
2015-10-26 7:41 ` Sebastian Gniazdowski
2015-10-26 7:47 ` Sebastian Gniazdowski
2015-10-24 6:27 ` Sebastian Gniazdowski
2015-10-24 10:54 ` Sebastian Gniazdowski
2015-10-24 11:25 ` Sebastian Gniazdowski
2015-10-24 16:31 ` Bart Schaefer
2015-10-24 16:41 ` Bart Schaefer
2015-10-23 6:32 ` Sebastian Gniazdowski
2015-10-16 0:37 ` Bart Schaefer
2015-10-13 13:07 ` Sebastian Gniazdowski
2015-10-13 13:31 ` Sebastian Gniazdowski
2015-10-12 12:05 ` Sebastian Gniazdowski
2015-10-12 15:13 ` Bart Schaefer
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