On Wed, Oct 17, 2007 at 10:11:36AM -0400, Christopher Schultz wrote: > > Second strange case: > > When I start tomcat using /opt/tomcat/bin/catalina.sh start, I get 21 > > processes that running the same command(different PIDs). And my tomcat > > instance seems to run fine without problem. When I kill one of the > > process, the rest will go down as well. > > You are seeing each thread as a Linux process. This is perfectly fine > depending on the kernel version (can't remember which ones do what). > Linux uses processes to model threads, so it's nothing to worry about.
It's a little more complex than that. Linux recognizes this overarching abstraction called a Context of Execution. Two COEs that have the same virtual address space are what most people would think of as "threads". A "process" is the set of all COEs sharing a given virtual address space. Apparently the thing that 'ps' is looking at is actually a table of COEs, not processes. To make things more fun, different versions of 'ps' work differently. procps v3 by default coalesces all of a process' threads into a single line, but 'ps -eLf' will show individual threads. IIRC procps v2 shows individual threads by default, and I don't recall whether it has the option of coalescing them. For still more fun, procps forked between v2 and v3, so it's possible you are still getting fresh updates of procps v2. At one point I had one Tomcat running on Red Hat Linux and another on Gentoo Linux, and one showed a huge number of Tomcat "processes" while the other showed only one. Switching attention between the two was, uh, interesting. -- Mark H. Wood, Lead System Programmer [EMAIL PROTECTED] Typically when a software vendor says that a product is "intuitive" he means the exact opposite.
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