On Fri, Feb 19, 2016 at 6:00 PM, Dmitry V. Levin <l...@altlinux.org> wrote: > Hi, > > On Fri, Feb 19, 2016 at 05:47:40PM +0530, haris iqbal wrote: >> Hello. >> >> I was going through the code of strace.c, when I found this line in >> init() function. >> >> tcbtabsize = argc; /* Surely enough for all -p args. */ > >> That set me thinking is it really is what I think it is. Can it really >> be that strace will allocate that many tcbtab pointers and tcp >> structures as many arguments I give to the program. > > The fun of the situation is that after commit v4.6-258-ge8172b7 > this is no longer enough for all -p args. > >> So I set out to find out whether there is a way to make strace take a >> lot of memory, without actually using it. >> >> Firstly I found out that if there is a way to give large number of >> arguments and still make strace work as it should. It turns out that >> there is. One can give as many -i (or some other such arguments) as >> arguments and the strace would work properly. >> >> Then, I wanted to make sure whether the code is actually allocating >> that many resources as as there are arguments. So I went into the >> cleanup() function that is called through error_msg_and_die(). And >> there I added debugging code to see how many of them were actually >> allocated. It turns out that they were allocated. >> I added a print statement in the for loop of cleanup(). It ran for as >> many number of times as there were arguments. Although the usefull one >> was the first one only, which had the pid of the process being traced >> (strace was run with -p <pid> option). >> >> So, summing it all up. I ran a script which gave strace a -p option >> and a process pid to trace. Along with that some 600000 -i options. It >> ran successfully with a memory consumption of around 100mb. Thats a >> lot for a small system with limited memory. > > OK, so what would you suggest to change in initial tcb table allocation?
There are still many portions of code which I have not understood properly, but I am to make a suggestion with whatever knowledge I have of the code. I would say to postpone the allocation till alloctcb() is called. But I can see many places where alloctcb() is called is by checking whether tcp->pid is present or not. And for that check, one would need an allocated structure with a 0 value. Are we allocating tcb table for multiple -p options only or does it have some other purpose? > > > -- > ldv > > ------------------------------------------------------------------------------ > Site24x7 APM Insight: Get Deep Visibility into Application Performance > APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month > Monitor end-to-end web transactions and take corrective actions now > Troubleshoot faster and improve end-user experience. Signup Now! > http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 > _______________________________________________ > Strace-devel mailing list > Strace-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/strace-devel > -- With regards, Md Haris Iqbal, Placement Coordinator, MTech IT NITK Surathkal, Contact: +91 8861996962 ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 _______________________________________________ Strace-devel mailing list Strace-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/strace-devel
