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From Igor Sysoev ...@rambler-co.ru>
Subject RE: Allocating a buffer efficiently...?
Date Sat, 02 Mar 2002 15:41:20 GMT
On Sat, 2 Mar 2002, Sander Striker wrote:

> > In a recent patch to mod_proxy, a static buffer used to store data read
> > from backend before it was given to frontend was changed to be allocated
> > dynamically from a pool like so:
> > 
> > +    /* allocate a buffer to store the bytes in */
> > +    /* make sure it is at least IOBUFSIZE, as recv_buffer_size may be
> > zero for
> > system default */
> > +    buf_size = MAX(recv_buffer_size, IOBUFSIZE);
> > +    buf = ap_palloc(r->pool, buf_size);
> > 
> > This change allows for a dynamically configurable buffer size, and fixes
> > the code to be thread safe.
> > 
> > However: it has been pointed out that this new code makes the Apache
> > footprint significantly larger like so:
> > 
> > > There is one drawback in this code. ap_palloc() is not good for
> > > big allocations (I think > 16K) because it stores data and meta-data
> > > together. I had found this when try to allocate memory from pool
> > > for zlib in mod_deflate. zlib needs about 390K - 2*128K + 2*64K + 6K.
> > > After this change Apache had grown up about 2M after about hour
> > > with 50 requests/s. I'm not sure that this growing could continue but
> > > I did not want additional 2M on each Apache.
> 
> Can you point me to the original post?  I'd like to see the context.
> Specifically which pool is being used.

You see all context - Graham have quoted almost whole my email.
As to pool I had tried to make big allocation from
r->connection->client->pool. Keep-alives were off.

> > > I use malloc for big allocations, store addresses in array
> > > allocated from pool and set cleanup for this array.
> > > In cleanup I free addresses if they is not free already.
> > 
> > Comments...?

Igor Sysoev


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