From: Han Pingtian <hanpt@linux.vnet.ibm.com>
To: zsh-users@zsh.org
Cc: schaefer@brasslantern.com
Subject: Re: argv subscript range uses too many memory
Date: Tue, 20 Nov 2012 21:04:57 +0800 [thread overview]
Message-ID: <20121120130457.GD2500@localhost.localdomain> (raw)
In-Reply-To: <121110065709.ZM4781@torch.brasslantern.com>
On Sat, Nov 10, 2012 at 06:57:09AM -0800, Bart Schaefer wrote:
> Further discussion probably should be re-routed to zsh-workers.
>
> On Nov 10, 6:58pm, Han Pingtian wrote:
> }
> } Looks like when running with 'print -- "$argv[1,3]", the call trace is
> } something like this:
> }
> } (gdb) bt
> } #0 mmap_heap_alloc (n=0x7fff0852e880) at mem.c:449
> } #1 0x000000000045f5f9 in zhalloc (size=1594456) at mem.c:542
> } #2 0x00000000004a4dfa in arrdup (s=0x313b008) at utils.c:3648
> } #3 0x0000000000471fa9 in getarrvalue (v=0x7fff0852ea20) at params.c:2174
>
> Ah, yes. Array slices are implemented by copying the entire array and
> then extracting the desired subset from the copy. Individual array
> elements are string references and therefore copy only the one element.
>
> Unfortunately this is pretty deeply ingrained in zsh's parameter
> expansion implementation and likely requires some serious rewriting to
> fix. It might be easier to come up with a way to garbage-collect more
> frequently.
>
> In a loop, the heap allocations are not popped until the loop is done,
> IIRC, so you'll end up with a large number of copies of the original
> array in the heap with slice results pointing into different parts of
> each copy. Maybe there's a narrower scope in which a pushheap/popheap
> could be inserted.
Looks like I have found the reason of this problem. If I revert this commit:
commit 61505654942cb9895a9811fde1dcbb662fd7d66a
Author: Bart Schaefer <barts@users.sourceforge.net>
Date: Sat May 7 19:32:57 2011 +0000
29175: optimize freeheap
Then the problem will be fixed. Please have a look. Thanks.
next prev parent reply other threads:[~2012-11-20 13:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-08 8:40 Han Pingtian
2012-11-08 10:02 ` Peter Stephenson
2012-11-10 10:58 ` Han Pingtian
2012-11-10 14:57 ` Bart Schaefer
2012-11-20 13:04 ` Han Pingtian [this message]
2012-11-20 17:03 ` Bart Schaefer
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