Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:28908
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: error (pb1.pair.com: domain tekrat.com from 204.15.23.157 cause and error)
In-Reply-To: <7cea347c0704160319x619b26d0s7716e35493e122c4@mail.gmail.com>
References: <7cea347c0704160319x619b26d0s7716e35493e122c4@mail.gmail.com>
Mime-Version: 1.0 (Apple Message framework v752.3)
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
Message-ID: <E852B9E8-5F51-4092-8C34-D28A0B45795B@tekrat.com>
Cc: internals@lists.php.net
Content-Transfer-Encoding: 7bit
Date: Tue, 17 Apr 2007 12:57:47 -0700
To: David Sklar <david.sklar@gmail.com>
Subject: Re: [PHP-DEV] Trapping "memory exhausted" error
From: shire@tekrat.com (Brian Shire)


I have code at Facebook that currently does something similar by  
catching fatal errors but there's a lot of gotcha's obviously that  
need to be handled properly when the engine is in this state.  When  
possible we enable the printing of backtraces and other debug  
information, however you run the risk that instead of a nice  
backtrace you get a nice "Segmentation fault" error instead.  This  
can be wrapped up in an extension and is all C code functionality,  
not exactly a soft memory limit so it's a little different than  
what's being discussed, but it might be another option to what you're  
looking for.  I'm happy to share with a few initially who would find  
it useful/give feedback.

-shire

On Apr 16, 2007, at 3:19 AM, David Sklar wrote:

> I am interested in being able to trap the (currently) fatal error that
> results when memory usage exceeds the defined memory limit.
>
> I was thinking it could work as follows:
>
> - in addition to a memory_limit configuration directive, there could
> be a "memory_limit_grace" configuration directive. This gets stored in
> the struct _zend_mm_heap, along with the limit.
>
> - Also added to struct _zend_mm_heap is a "initial limit reached" flag
>
> - When zend_mm_safe_error() in Zend/zend_alloc.c is invoked under the
> current conditions (memory_limit exceeded), it sets the "initial limit
> reached" flag, adjusts the heap limit to the "memory_limit_grace"
> value and throws some non-fatal error (or an exception if it is
> feasible from here.)
>
> - When zend_mm_safe_error() is invoked and the "initial limit reached"
> flag is already set, it throws the fatal error exactly as it does now.
>
> This "grace period" would provide a way to gracefully exit when a
> memory limit is reached, but also has the hard limit still enforced so
> that code which is supposed to be gracefully exiting doesn't chew up
> too much additional memory.
>
> Is it feasible to adjust the heap limit and throw a non-fatal error
> from within zend_mm_safe_error()?
>
> David
>
> -- 
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>