Re: Understanding memory fragmentation in Linux kernel
On 31/12/2018 07:28, Amit Agarwal wrote: > I am not requesting help in resolving the issue with application (I will > be able to debug that), but only need help in understanding the memory > fragmentation part. ( I gave details of original problem so that I can > explain what I am trying to understand and why). To get a deeper understanding of memomry managment (and fragmentation) on linux I would recommend the Memory Managment case study chapter of "Modern Operating Systems" from Andrew S Tanenbaum. It has a own Case Study Study Part with Chapters for several modern Operating Systems, one being Linux. There it covers its Memory managment in nice detail. Thanks, -- Richard signature.asc Description: OpenPGP digital signature ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Understanding memory fragmentation in Linux kernel
On Sun, 2018-12-30 at 22:54 -0800, Manish Katiyar wrote: > > Maybe you can try > > echo m > /proc/sysrq-trigger I will check this and see if this can provide something useful for me. Did not know about this. > > Or looking at /proc/buddyinfo I looked at buddyinfo and hence asked for more documentation on that. Does the pages that buddyinfo list under any "order at" are contigeous or are they located somewhere in memory? For ex: If buddyinfo shows 2 pages for 0th order, does it mean that there are 2 contigeous pages of 2M each? > -- Thanks, -aka ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Understanding memory fragmentation in Linux kernel
On Sun, Dec 30, 2018, 10:28 PM Amit Agarwal On 2018-12-31 06:22, Manish Katiyar wrote: > > > How do you know it is because of memory ? If you have sufficient RAM then > it should be able to allocate. Does you application fail with ENOMEM ? > Without knowing the error code from application it's hard to suggest > anything. > > > There is no debugging enabled on site and there is nothing we can do now > to enable it and it is happening in only one site. But from whatever logs I > have, it is failing in calloc. > > I am not requesting help in resolving the issue with application (I will > be able to debug that), but only need help in understanding the memory > fragmentation part. ( I gave details of original problem so that I can > explain what I am trying to understand and wh > Maybe you can try echo m > /proc/sysrq-trigger Or looking at /proc/buddyinfo > > -- > Thanks, > -aka > ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Understanding memory fragmentation in Linux kernel
On 2018-12-31 06:22, Manish Katiyar wrote: > How do you know it is because of memory ? If you have sufficient RAM then it > should be able to allocate. Does you application fail with ENOMEM ? > Without knowing the error code from application it's hard to suggest anything. There is no debugging enabled on site and there is nothing we can do now to enable it and it is happening in only one site. But from whatever logs I have, it is failing in calloc. I am not requesting help in resolving the issue with application (I will be able to debug that), but only need help in understanding the memory fragmentation part. ( I gave details of original problem so that I can explain what I am trying to understand and why). -- Thanks, -aka___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Understanding memory fragmentation in Linux kernel
On Sun, Dec 30, 2018, 10:03 PM Amit Agarwal Hi All, > > > I am trying to understand memory fragmentation and how to understand > and/or analyze the same. > > Is there some detailed documentation on pagetypeinfo and buddyinfo files > present in the proc directory? Am I looking at right files to understand if > the memory is fragmented. > > > Problem Description: > > One of the applications does a few 200-300Mb calloc's during start-up. On > one of the production servers, the application does not start up although > there should be enough RAM available for application to start. I am > suspecting that this is because of fragmentation and would like to confirm > the same. > How do you know it is because of memory ? If you have sufficient RAM then it should be able to allocate. Does you application fail with ENOMEM ? Without knowing the error code from application it's hard to suggest anything. -- > Thanks, > -aka > ___ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
