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Posted to dev@httpd.apache.org by "William A. Rowe, Jr." <wr...@covalent.net> on 2002/10/14 00:37:26 UTC
HTTP EnableSendfile directive and new mechanics
To both lists, since this patch affects APR and sendfile.
The attached patch introduces the EnableSendfile directive for httpd. Jeff and
I have seen several cases, including NFS shares and so forth, that are not
compatible with apr_sendfile. It works similarly to EnableMMAP but the
differences are worth discussing. {This is why I'm posting and not yet ready
to commit.}
The EnableMMAP worked by adding a flag to the bucket. However, it seems
very silly to do so when what we really want to toggle is the file.
We also have an issue on Win32, we weren't using the correct open file semantics.
This may have had something to do with BSoD (kernel panic) using some socket
drivers on Win32. Opening for TransmitFile should be done with sequential
optimizations and I believe it must be opened overlapped (that XTHREAD flag.)
But the XTHREAD flag means more than just sendfile - it means multiple threads
will need atomic seek-read/write operations on all platforms. That wasn't the
right flag to play with across the board.
So this patch proposes an APR_OPEN_FOR_SENDFILE bit, where that bit
has little impact on any platform but Win32.
BUT - it does act as a sentinal that we can sendfile the flag. This allows us, at
the apr_file_t granularity, to choose to sendfile or not. It also can get rid of some
nasty side effects like Win9x which can't sendfile. We decide this at runtime, so
we will simply unset that flag if requested.
Finally, we already have the semantics to recover the flags value from an apr_file_t,
giving the HTTP core output filter the final word to sendfile or not to sendfile.
Comments welcome, I'll commit midweek if nobody hollers.
Bill
Re: HTTP EnableSendfile directive and new mechanics
Posted by "William A. Rowe, Jr." <wr...@apache.org>.
At 12:50 PM 10/14/2002, Jeff Trawick wrote:
>"William A. Rowe, Jr." <wr...@covalent.net> writes:
>
>> The attached patch introduces the EnableSendfile directive for httpd. Jeff and
>> I have seen several cases, including NFS shares and so forth, that are not
>> compatible with apr_sendfile. It works similarly to EnableMMAP but the
>> differences are worth discussing. {This is why I'm posting and not yet ready
>> to commit.}
>
>looks reasonable to me...
>
>since on Win32 APR actually needs to know if it can be sendfile-ed at
>apr_file_open time, I guess that makes apr_file_t the winner in the
>contest of where to save the fact that Apache doesn't want sendfile to
>be used
Actually ... we could have performed exactly the same magic for MMAP
to make the transition from the per_dir_conf context across to the brigade
dynamics. This would have eliminated the need to have a bucket flag
to support MMAP, since we already have this handy per-file flags entity
that is passed from the default_handler across to the core_output_filter.
Bill
Re: HTTP EnableSendfile directive and new mechanics
Posted by "William A. Rowe, Jr." <wr...@apache.org>.
At 12:50 PM 10/14/2002, Jeff Trawick wrote:
>"William A. Rowe, Jr." <wr...@covalent.net> writes:
>
>> The attached patch introduces the EnableSendfile directive for httpd. Jeff and
>> I have seen several cases, including NFS shares and so forth, that are not
>> compatible with apr_sendfile. It works similarly to EnableMMAP but the
>> differences are worth discussing. {This is why I'm posting and not yet ready
>> to commit.}
>
>looks reasonable to me...
>
>since on Win32 APR actually needs to know if it can be sendfile-ed at
>apr_file_open time, I guess that makes apr_file_t the winner in the
>contest of where to save the fact that Apache doesn't want sendfile to
>be used
Actually ... we could have performed exactly the same magic for MMAP
to make the transition from the per_dir_conf context across to the brigade
dynamics. This would have eliminated the need to have a bucket flag
to support MMAP, since we already have this handy per-file flags entity
that is passed from the default_handler across to the core_output_filter.
Bill
Re: HTTP EnableSendfile directive and new mechanics
Posted by Jeff Trawick <tr...@attglobal.net>.
"William A. Rowe, Jr." <wr...@covalent.net> writes:
> The attached patch introduces the EnableSendfile directive for httpd. Jeff and
> I have seen several cases, including NFS shares and so forth, that are not
> compatible with apr_sendfile. It works similarly to EnableMMAP but the
> differences are worth discussing. {This is why I'm posting and not yet ready
> to commit.}
looks reasonable to me...
since on Win32 APR actually needs to know if it can be sendfile-ed at
apr_file_open time, I guess that makes apr_file_t the winner in the
contest of where to save the fact that Apache doesn't want sendfile to
be used
--
Jeff Trawick | trawick@attglobal.net
Born in Roswell... married an alien...
Re: HTTP EnableSendfile directive and new mechanics
Posted by Jeff Trawick <tr...@attglobal.net>.
"William A. Rowe, Jr." <wr...@covalent.net> writes:
> The attached patch introduces the EnableSendfile directive for httpd. Jeff and
> I have seen several cases, including NFS shares and so forth, that are not
> compatible with apr_sendfile. It works similarly to EnableMMAP but the
> differences are worth discussing. {This is why I'm posting and not yet ready
> to commit.}
looks reasonable to me...
since on Win32 APR actually needs to know if it can be sendfile-ed at
apr_file_open time, I guess that makes apr_file_t the winner in the
contest of where to save the fact that Apache doesn't want sendfile to
be used
--
Jeff Trawick | trawick@attglobal.net
Born in Roswell... married an alien...