Wireshark mailing list archives
Re: RFD: The Future of Memory Management in Wireshark
From: Sébastien Tandel <sebastien.tandel () gmail com>
Date: Fri, 26 Oct 2012 11:29:15 -0200
On Wed, Oct 24, 2012 at 11:13 AM, Evan Huus <eapache () gmail com> wrote:
On Wed, Oct 24, 2012 at 8:10 AM, Sébastien Tandel <sebastien.tandel () gmail com> wrote:On Wed, Oct 24, 2012 at 1:10 AM, Guy Harris <guy () alum mit edu> wrote:On Oct 18, 2012, at 6:01 PM, Evan Huus <eapache () gmail com> wrote:I have linked a tarball [2] containing the following files: - wmem_allocator.h - the definition of the allocator interface - wmem_allocator_glib.* - a simple implementation of the allocator interface backed by g_malloc and a singly-linked list.Presumably an implementation of the allocator could, instead of callingalower-level memory allocator (malloc(), g_malloc(), etc.) for each allocation call, allocate larger chunks and parcel out memory from the larger chunks (as the current emem allocator does), if that ends upsavingenough CPU, by making fewer allocate and free calls to the underlyingmemoryallocator, so as to make it worth whatever wasted memory we have at theendsof chunks?One step further, instead of mempools, I think wireshark could have great interest in implementing slabs (slab allocator). Slabs had initially been designed for kernel with several advantages over traditional allocatorsinterms of resources needed to allocate (CPU), (external / internal) fragmentation and also cache friendliness (most of the traditional allocators don't care). I've attached some slides about a high-level description of slab. Since then, another paper has been written showing some improvements and what it took to write a slab for user-space (libumem). There is another well-known exampel out there, called memcache, that implements its own version (and could be a good intial point for wireshark implementation,whoknows? :))If I understand correctly, a slab allocator provides the most benefit when you have to alloc/free a large number of the same type of object,
you're right, that's where slab is the most efficient at. Although, the second paper shows it can be efficient for general purpose allocation based on size and not specific structure. but I don't know if this is necessarily the case in Wireshark. There
are probably places where it would be useful, but I can't think of any off the top of my head. TVBs maybe? I know emem is currently used all over the place for all sorts of different objects...
I guess the most obvious would be emem_tree (emem_tree_node) might be an example used all over and over while dissecting. :) There is indeed a bunch of different objects allocated with emem. Also, it might be used to allocate memory for some fragments. Since your interface seems to allow it, we could create several slabs types, one for each specific structures that are allocated very frequently (emem_tree_node?), others for packets/fragments with some tuned slabs sizes and another with some generic sizes. You could certainly shoehorn a slab allocator into wmem's current
architecture, but you'd have to abuse the wmem_allocator_t interface to do it. I suspect that it would make more sense to implement slabs separately anyways - since their goal is primarily performance you would want to cut out the function pointers that wmem currently uses. It's definitely worth thinking about though. Thanks, Evan ___________________________________________________________________________ Sent via: Wireshark-dev mailing list <wireshark-dev () wireshark org> Archives: http://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev mailto:wireshark-dev-request () wireshark org ?subject=unsubscribe
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Current thread:
- RFD: The Future of Memory Management in Wireshark Evan Huus (Oct 18)
- Re: RFD: The Future of Memory Management in Wireshark Guy Harris (Oct 23)
- Re: RFD: The Future of Memory Management in Wireshark Evan Huus (Oct 23)
- Re: RFD: The Future of Memory Management in Wireshark Sébastien Tandel (Oct 24)
- Re: RFD: The Future of Memory Management in Wireshark Evan Huus (Oct 24)
- Re: RFD: The Future of Memory Management in Wireshark Sébastien Tandel (Oct 26)
- Re: RFD: The Future of Memory Management in Wireshark Evan Huus (Oct 26)
- Re: RFD: The Future of Memory Management in Wireshark Graham Bloice (Oct 26)
- Re: RFD: The Future of Memory Management in Wireshark Evan Huus (Oct 26)
- Re: RFD: The Future of Memory Management in Wireshark Sébastien Tandel (Oct 26)
- Re: RFD: The Future of Memory Management in Wireshark Evan Huus (Oct 26)
- Re: RFD: The Future of Memory Management in Wireshark Sébastien Tandel (Oct 26)
- Re: RFD: The Future of Memory Management in Wireshark Guy Harris (Oct 23)
- Re: RFD: The Future of Memory Management in Wireshark Evan Huus (Oct 25)
- Re: RFD: The Future of Memory Management in Wireshark Jeff Morriss (Oct 25)
- Re: RFD: The Future of Memory Management in Wireshark Evan Huus (Oct 25)