-----Original Message----- From: fedora-list-bounces@xxxxxxxxxx [mailto:fedora-list-bounces@xxxxxxxxxx] On Behalf Of James Foris Sent: Monday, July 26, 2004 3:22 PM To: fedora-list@xxxxxxxxxx Subject: Memory Performance Issue with Fedora Core 2 Kernels ...[snip]... >My driver requires a large amount of contiguous physical memory for >DMA from a PCI device. I use the 'mem=YYY' command line parameter to >reserve the top of physical RAM for my driver. Then I allow mapping >via mmap() calls to user space. The user space app then uses this >pointer to save the data to disk. >Normally the user space app writes to disk using the mmap()'d pointer as >the source. With the new kernels these writes are taking way too long >(around 20 MB/s). Even when the write goes to /dev/shm, the speed is >limited to around 20 MB/s. A memcpy from the mmap()'d memory seems to >have no such slowdown. The bottleneck seems to be in i/o... check the hdparm settings on the drive. (memcpy will definitely run faster than disc i/o) ...[snip]... -- fedora-list mailing list fedora-list@xxxxxxxxxx To unsubscribe: http://www.redhat.com/mailman/listinfo/fedora-list
