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1d
comment How to detect if USB device is bootable in udev?
You can run a script on a udev rule trigger. The trick would be for your script to scan the first few bytes of the disk for an MBR signature. The solution given by Nasha above is acceptable. Alternatively, roll your own one liner using dd and perl /grep to scan the first sector of the usb disk for an MBR signature.
1d
comment Does anyone actually use and benefit from transparent huge pages?
The main painpoint with HugePages seesm to be NUMA related. Practically every new shiny multiprocessor server out there is now NUMA enabled. Funky things in the memory subsystem ensue once you have huge pages that cross NUMA boundaries. Have a look at: engineering.linkedin.com/performance/…
1d
comment Docker says “no space left on device” but, system has plenty of space?
Docker is extracting a tar file from /var/lib/docker/tmp/70.... to a directory under /var/lib/docker/devicemapper/.... The fact that there's the substring 'devicemapper' in that path makes me think that docker is mapping some block storage device into a docker specific block device for use. This probably means that if you run lsblk/df and friends before or after the docker command, you'll miss the mapped device (docker cleans up after itself?). I'd propbably ctrl-z the unbundling process after the errors start popping and start poking around with df/dm tools. Can you do that?
Apr
17
comment Fixing terrible performance when watching/reading video and writing video files to disk
If you have source code access to the downloader, see whether using memory mapped files would help. I'd try: 1. Use the deadline scheduler. 2. Try to bunch up your writes into few large consecutive writes instead of many small writes (IOPS vs Throughput). 3. Tell your downloader to stop abusing the vm cache (posix fadvise). 4. ionice the downloader to a lower priority and the reader process to a higher priority. 5. Have a look at /prov/sys/vm/[dirty-ratio, dirty_bytes]. Playing with this variable will influence your writeback behaviour. linuxinsight.com/proc_sys_vm_dirty_bytes.html
Apr
17
comment Fixing terrible performance when watching/reading video and writing video files to disk
Have you tried looking at the VM subsystem hints? POSIX fadvise that is? You may find that the download process is trashing your VM cache. Download linux-ftools and wrap the download/write to disk script with fadvise dontneed and see what happens. code.google.com/p/linux-ftools
Apr
17
comment How to create a fake inotify event on debian?
Can you touch a zero sized hidden file? Say your media files are in /var/blah/media/pictures. Just touch a .touchme and that should generate the correct inotify event. Would this work?
Apr
17
comment What is the IPsec bottleneck in Linux?
Hmm, that is interesting. I'd suspect that something in the kernel is slowing things up. Would you mind sharing your ipsec configuration? I'd like to instrument a VM and see what results I'll get with different settings.
Nov
5
comment Disk is a bottleneck. Background processes make things worse. How to improve responsiveness?
YMMV: We did try to play around with swappiness unsuccessfully. We tried all kind of values, graphed stuff and didn't get anywhere. We eventually ended writing up a daemon that would evict the pages of certain misbehaving programs every few seconds from the page cache.
Nov
5
answered Dovecot/Postfix mail server replies to [SYN] with [RST, ACK] when user attempts to connect (POP3). Likely iptables?
Nov
5
answered First sudo always slow
Nov
5
awarded  Yearling
Nov
5
revised Disk is a bottleneck. Background processes make things worse. How to improve responsiveness?
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Nov
5
answered Disk is a bottleneck. Background processes make things worse. How to improve responsiveness?
Aug
20
answered Redirecting loopback traffic through a router
Jun
10
awarded  Populist
Aug
17
awarded  Yearling
Jul
28
awarded  Good Answer
Jun
21
awarded  Yearling
Nov
7
awarded  Nice Answer