RTimothyEdwards
`Running magic to create magic database files` takes too long
This appears to be a regression in a recent patch, but essentially, Running magic to create magic database files. takes 3x as much time as it used to. I'm not sure how this is happening, but it's greatly inflating PDK build times.
I need more information, as there is nothing updated recently that should be causing extra time here. But if it's a real effect, I want to know what happened.
I noticed a couple of magic processes were taking quite a while to complete. Not sure if it is the same issue @donn is seeing, but a profile shows:
Samples: 102K of event 'cycles', Event count (approx.): 119046649203
Overhead Command Shared Object Symbol
89.35% magicdnull tclmagic.so [.] DBFullResidueMask
5.99% magicdnull tclmagic.so [.] lefWriteMacro
A wild guess, but we did add a call to DBFullResidueMask in lefWriteMacro in https://github.com/RTimothyEdwards/magic/commit/ee1d1ae5b0219c272edd4775dccaa3e39647f381
@antonblanchard : That appears to be the result of running "lef write" on a layout with a huge number of labels, a pretty specific case.
The slow magic process is called from 'make io-A' and when I strace it, it is writing out incredibly slowly (1 write every second):
22:29:14.845929 write(4, "END\n PORT\n LAYER met3 ;\n"..., 4096) = 4096
22:29:15.906640 write(4, " RECT 67.530 198.785 67.850 199"..., 4096) = 4096
22:29:17.051336 write(4, " END\n PORT\n LAYER met"..., 4096) = 4096
22:29:18.154393 write(4, "30 197.975 66.650 198.295 ;\n "..., 4096) = 4096
22:29:19.247822 write(4, "65.900 28.060 66.100 28.260 ;\n "..., 4096) = 4096
It does seem to be specific to the overlay cells. sky130_fd_io__overlay_vssio_hvc has thousands of entries for pin VSSIO. The LEF file for that one I/O cell takes up 10% of the output LEF library.
The LEF library should not contain the overlay cells, anyway, just the top level cells. I can change the build process to put only the top level I/O cells in the LEF library.