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SubjectRe: Poll and Select not scaling
On Wed, 10 Jan 2001, Dan Kegel wrote:

> select() is usually limited to 1024 file descriptors

oh hey, this limit is only a libc limit these days. you can do this:

#define MY_FD_SETSIZE (16384)
typedef struct {
__fd_mask __fds_bits[MY_FD_SETSIZE / __NFDBITS];
} my_fd_set;
#define MY_FD_ZERO(_f) (memset((_f), 0, sizeof(my_fd_set)))

and do select()s of 16384 descriptors.

> poll() is a slightly better choice. However, although
> it can handle 30000 file descriptors, the performance sucks;
> see http://www.kegel.com/dkftpbench/Poller_bench.html#results

poll() stops working at 16384 file descriptors (as of 2.2.14-foo original
redhat 6.2 kernel). at least that's where i think it is, maybe it's
32768. it's limited by the maximum kmalloc() size of 128k. this is
somewhat unfortunate. even though we know it'll stop performing well.

-dean

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