Hi, all, I am trying to instrument linux-2.2.19 kernel to measure the number of times each page is read. That is, for each page that is read by each process from disk, there should be a counter. Once the measurement started, the number of times a page is read from disk by a process should be counted; if page is written out to swap space and brought back in, this should be included in the count. Intially, it occured to me that maintaining the information needed to asscociate disk locations with virtual addresses within the kernel will be difficult.(possibly requiring the use of has tables, etc.) and I was afraid to change things in obscure ways. Instead, I was using another approach, namely to let kernel only output a log of all the swap-ins and address mappings it performs, and leave it to a user program to complete the missing links. However, in this way, logging(using "syslogd" and "klogd") seriously gets in the way of measuring reads. It would increase disk I/O or disturb the workload. Especially, when workload is large, log file is also very big. This needs insance sized kernel log buffer. However when I modified the printk buffer to 4Mb, system can't even boot up. Also sometimes, I got garbled lines in log, which may due to differences in processor speed and harddisk speed. I was considering to invent a new logging facility, which is more optimized than "klogd". But it seemed that to reduce interference, I may need to redirect logs to a harddisk situated on a different harddisk controller, like SCSI. This requires additional hardware...very troublesome. Right now, I am stuck here and deciding whether to improve logging approach, or try another new way. That's why I am here to ask you to give me some suggestions. The aim is just to measure the number of each page is read when runing a process. Btw, is it feasible to use or introduce some additional bits in process page-table to accomplish this? If so, could you show me some pointers?? Thanks in advance! -- Cheers! Zou Min - Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ IRC Channel: irc.openprojects.net / #kernelnewbies Web Page: http://www.kernelnewbies.org/
