Steven Dake napsal(a): > On 07/08/2010 06:39 AM, Jan Friesse wrote: >> Steven Dake wrote: >>> In a recent patch to validate that shared memory is actually available >>> for use, Angus used a write call with 64 byte writes at a time to >>> validate the space was available before mmap()ing. This results in alot >>> of write() syscalls which is slowing down ipc connection creation. >>> >>> This patch uses a page sized write() call. >>> >>> Regards >>> -steve >>> >>> >>> ------------------------------------------------------------------------ >>> >>> _______________________________________________ >>> Openais mailing list >>> Openais@lists.linux-foundation.org >>> https://lists.linux-foundation.org/mailman/listinfo/openais >> >> Steve, >> >> >> + } >> + memset (buffer, 0, page_size); >> + for (i = 0; i< (bytes / page_size); i++) { >> retry_write: >> >> Seems correct, but it isn't. Let's say, page_size is 4096 and you want >> preallocate 4093 bytes. Code will not work as expected. >> > > bytes should always be a multiple of the page size, resulting in a > correct division every time.
Should be and in current code really is. > > How does a user preallocate 4093 bytes? > Problem is, that coroipcc_service_connect is public API, so user/developer can call it with request_size 4093 bytes. Also from API perspective (even internal) it's not so bad idea to somehow deal with weird situations like that and it really doesn't matter too much if dealing is "make it correctly" or return -1 if bytes % page_size != 0. Regards, Honza > Regards > -steve > >> Take a look to my patch for whitetank, where exactly this is solved. >> >> Regards, >> Honza > _______________________________________________ Openais mailing list Openais@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/openais
